Application Ideas
What could you build?
59 things worth building, from a page you finish this afternoon to firmware on a chip. Open any one for the three or four ways you could actually build it, from the version that is barely software to the one that is a real project, and what each choice costs you.
Filter by what kind of software it is, or go back to the 24 types of applications those colours mean.
Colours mean Static & content Runs in the browser Database-backed Automation AI-powered Mobile & offline Desktop, CLI & extensions Games Hardware & IoT
Personal website
One page that is yours, at an address you own, that outlives every platform.
What it is
A small site about you — what you do, what you have made, how to reach you. A few paragraphs, some links, maybe a photo.
How you can build it
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1 One hand-written page
A single HTML file with your name, what you do, and some links, pushed to a free static host on your own domain.
- Live this afternoon, free forever
- Nothing to update, patch, or pay for
- Loads instantly anywhere on earth
- Every change means opening a code editor
- No structure once you want more than a few pages
Learn more about Very simple static website
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2 A static site generator
The same output, but with shared layouts and pages written in markdown, so the header exists once rather than on every page.
- Adding a page is writing a file
- Layouts and styling stay in one place
- A build step and a toolchain to keep working
- Overkill under about five pages
Learn more about Very simple static website
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3 Add a CMS once you post regularly
Keep the static output and put an editor screen in front of it, so writing does not require a code editor.
- Publish from a phone or a borrowed laptop
- Still free, still static, still fast
- A second thing to set up and keep authenticated
- Not worth it if you edit twice a year
Learn more about Static site with a CMS
Portfolio or photography site
The work, large, with as little between the visitor and it as possible.
What it is
A site whose entire job is showing work — projects, photographs, writing, designs — with enough context on each piece to make it legible.
How you can build it
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1 Hand-built gallery of files
Images and project pages committed alongside the site, resized before they go in.
- Complete control over how each piece is presented
- No monthly cost and no platform rules
- Adding a project is a commit and a deploy
- You own the image resizing discipline
Learn more about Very simple static website
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2 Static site plus a CMS
Projects become content entries with an upload field, so publishing a new piece is filling in a form.
- Non-technical collaborators can add work
- Image handling and resizing come with the CMS
- Content model has to be decided up front
- One more service in the chain
Learn more about Static site with a CMS
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3 Database-backed with client areas
Only worth it when clients need private galleries, proofing, or downloads behind a login.
- Private galleries per client
- Track what has been viewed or approved
- Real running costs and real maintenance
- Far more machinery than a portfolio usually needs
Learn more about Web application with a database
Blog
The canonical reason to add a CMS — publishing has to be easy or it stops.
What it is
A site with a stream of dated posts, each with a title, a body, and tags, plus an index, tag pages, and a feed.
How you can build it
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1 Markdown files in the repo
Posts as files with a title and a date, rendered into an index and a page each at build time.
- Posts are plain text you will still be able to read in twenty years
- Free hosting, and version history for every edit
- Publishing needs a code editor and a commit
- Nobody else can post without repo access
Learn more about Very simple static website
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2 Static site plus a git-based CMS
The same markdown files, written through an admin screen that commits them for you.
- Write and publish from anywhere, no code editor
- Still static, so still free and unbreakable
- Publishing waits on a rebuild, usually under a minute
- The CMS is a second thing to configure
Learn more about Static site with a CMS
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3 A hosted blogging platform
Someone else runs the whole thing; you write. Worth being honest that this is often the right answer.
- Zero setup, built-in audience and distribution
- Comments, email, and analytics included
- The platform owns your address and can change the rules
- Your design is their design
Learn more about The one you might not need to build
Digital garden or notes site
Publish your notes as a linked web instead of a chronological stream.
What it is
A collection of short interlinked pages, each on one idea, growing and being revised continuously — no dates, no feed, no pressure to finish a thought.
How you can build it
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1 Markdown notes with wiki links
A folder of short notes that link to each other by name, rendered as one page per note with backlinks computed at build time.
- Notes stay plain files, usable in any editor
- Backlinks are a build-time calculation, not a database
- Renaming a note can break links unless the build checks
- No search without extra work
Learn more about Very simple static website
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2 Publish from a notes app
Keep writing where you already write, and run a job that exports the public subset into the site.
- No change to your daily writing habit
- Publishing becomes automatic rather than a decision
- The export is a pipeline that will break
- Deciding what is public needs a convention you never forget
Learn more about Automation that runs without you
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3 A live searchable app
Only once the collection is large enough that reading needs querying rather than browsing.
- Real search and filtering across hundreds of notes
- Can support drafts, private notes, and multiple authors
- A server and a database for what was a folder of text
- Loses the plain-files durability that made it appealing
Learn more about Web application with a database
Wedding or event site
Details, directions, and an RSVP — for a fixed date, then it is over.
What it is
A page with the when, the where, how to get there, where to stay, and a way to respond. It exists for a few months and then becomes a keepsake.
How you can build it
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1 One page and a form service
The details on a single page, with the RSVP going to a hosted form that writes to a spreadsheet you read.
- Up in an afternoon, free, nothing to maintain
- Guests need no account and no app
- Replies live in the vendor dashboard, not your site
- Editing the page means touching the file
Learn more about Static site that buys its backend
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2 A shared document or event platform
An event service or even a well-organised shared page. For eighty guests this genuinely works.
- Nothing to build, and reminders included
- Guest list and dietary requirements handled for you
- Their branding, their layout, their upsells
- No custom domain unless you pay
Learn more about The one you might not need to build
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3 A small app with a guest list
Personalised invites by link, so each household sees only their own seats and can amend their answer.
- Per-guest details without anyone logging in
- Amendments and reminders handled properly
- A database and a deploy for a three-month site
- Every hour on it is an hour not spent on the wedding
Learn more about Web application with a database
Restaurant or local business site
Hours, menu, phone number, map. Ninety per cent of visits want one of those four.
What it is
A small site for a physical business: what it is, when it is open, what it sells, where it is, and how to reach it — mostly viewed on a phone, mostly by people standing outside or deciding whether to come.
How you can build it
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1 One static page
Phone number, hours, address, and menu as real text — not a PDF — on a single fast page.
- Free, instant on a phone, and readable by search engines
- Nothing that can go down on a Friday night
- The owner cannot change the hours without you
- Holiday closing times will go stale
Learn more about Very simple static website
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2 Static site with a CMS for hours and menu
The parts that change often become content entries the owner edits from a phone.
- Wrong hours become the owner's problem to fix in a minute
- Menu changes need no developer
- Someone has to be trained and remember to use it
- A CMS to keep authenticated over years
Learn more about Static site with a CMS
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3 Add booking and ordering services
Reservations, ordering, and payments handled by specialists, embedded or linked from the page.
- Real capability without operating anything
- Payments and card details never touch your site
- A monthly fee per service, and they accumulate
- Checkout looks like the vendor, not the restaurant
Learn more about Static site that buys its backend
Documentation site
Structured reference material, searchable, versioned alongside the thing it documents.
What it is
A site of organised reference pages with a navigable hierarchy, search, and code examples — for a product, an internal system, or a process.
How you can build it
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1 Markdown in the same repo as the thing it documents
Nested folders become the sidebar; a change and its documentation travel in the same commit.
- Docs cannot drift from the code without someone noticing
- Free to host, and reviewable in pull requests
- Contributors need to be comfortable with git
- Search needs a build-time index once past about thirty pages
Learn more about Very simple static website
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2 A documentation framework
A generator built for this specific job, bringing navigation, versioning, and search with it.
- Search, versioned docs, and code samples out of the box
- Conventions decided for you
- You inherit the framework's opinions and upgrade cycle
- Customising past a point fights the tool
Learn more about Static site with a CMS
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3 Behind company sign-in
For internal documentation, where the content genuinely must not be public.
- Internal material can be candid
- Access follows the company directory
- The check has to be enforced on a server, not just a login screen
- One more system that can lock people out
Learn more about Static site with sign-in
Newsletter with an archive
Write once; it lands in inboxes and stays on the web.
What it is
A site holding every past issue as a page, a signup form, and a pipeline that turns publishing an issue into an email going out.
How you can build it
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1 A hosted email service, no site at all
Write in their editor, send to their list, use their public archive.
- Nothing to build, deliverability handled by experts
- Signup forms, analytics, and unsubscribes included
- The archive lives on their domain, not yours
- Their template, their footer, their pricing tiers
Learn more about The one you might not need to build
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2 Static archive plus a hosted sender
Issues live as markdown on your own site; the email service handles the list and the sending.
- Every issue is a real page on your domain, findable by search
- You keep the writing if you change providers
- Two places to publish unless you automate the second
- Email HTML and web HTML cannot share a stylesheet
Learn more about Static site with a CMS
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3 Publish once, send automatically
A job watches for a new issue on the site and pushes it to the email service as a campaign.
- One action publishes and sends
- The archive and the email can never disagree
- A pipeline that fails silently at the worst moment
- Email rendering quirks still have to be handled
Learn more about Automation that runs without you
Company website
Public-facing, edited by several people, and judged in about four seconds.
What it is
A marketing site: what the company does, for whom, proof it works, and a way to get in touch — maintained by marketing, not by engineering.
How you can build it
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1 Static site, one person edits it
Marketing pages built as files, changed by whoever owns the repo.
- Fastest possible pages, free hosting
- No accounts, no permissions, nothing to administer
- Marketing waits on a developer for every word change
- One person becomes a bottleneck and a risk
Learn more about Very simple static website
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2 Static site with a CMS behind sign-in
Named colleagues sign in with the company account and publish; the output stays static files.
- Several editors, each edit attributable
- Access is revoked by removing a person, not rotating a password
- Identity is the first genuinely hard concept here
- Somebody now owns the access list forever
Learn more about Static site with sign-in
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3 A website platform
A hosted builder. For a five-page marketing site with no engineering team, this is frequently the right call.
- Non-technical staff can change anything, immediately
- Hosting, forms, and analytics included
- Per-month cost that scales with nothing useful
- Performance and markup are the vendor's problem, and often bad
Learn more about The one you might not need to build
Landing page with a waitlist
Test whether anyone wants it before building it.
What it is
A single page describing a product that may not exist yet, with one field to capture an email address and a promise about what happens next.
How you can build it
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1 One page and a hosted form
A single page describing the product, with one email field posting to a form service.
- Live in an afternoon, no database, no accounts
- The list exports to CSV whenever you want it
- Confirmation emails need a second service
- No way to ask follow-up questions later
Learn more about Static site that buys its backend
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2 A form and spreadsheet, no page of your own
A hosted form is a page. Post the link directly and skip the site.
- Nothing to build at all
- Perfectly adequate for testing whether anyone cares
- No control over the pitch, which is what you are testing
- A form link is less credible than a real page
Learn more about The one you might not need to build
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3 Page plus an automated welcome sequence
Signups trigger an immediate confirmation and a scheduled update, so the list does not go cold.
- Sets expectations while interest is high
- Keeps a list warm for the months before launch
- An email service and its domain records to configure
- Sequences need writing, which is real work
Learn more about Automation that runs without you
Niche job board
One narrow field, curated listings, and employers who pay to post.
What it is
A site listing openings for one specific community, with a submission route for employers and a way for candidates to filter what they see.
How you can build it
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1 Curated by hand, static
You add each listing yourself; employers email you. Payment is a link you send before publishing.
- Proves demand before any software exists
- Curation is the product at small scale
- Every listing is your time
- Expiring old roles is a manual chore
Learn more about Very simple static website
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2 Static site with a submission form and payment link
Employers submit through a form and pay through a hosted checkout; you approve and publish.
- Revenue without building payments
- Approval step keeps quality up
- Two dashboards to reconcile against each other
- Still manual publishing
Learn more about Static site that buys its backend
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3 Accounts, self-service posting, and expiry
Employers manage their own listings behind a login, and postings expire on their own.
- Scales past what one person can curate
- Alerts, filtering, and search become possible
- Moderation and spam arrive with self-service
- Real running costs before there is real revenue
Learn more about Web application with a database
Internal company site
The handbook, the policies, the org chart — for people who already work here.
What it is
A private site holding the things everyone needs and nobody remembers: how to book leave, who owns what, the onboarding checklist, the expenses policy.
How you can build it
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1 A shared document folder
The policies and handbook in the company drive, well organised and genuinely indexed.
- Nothing to build, and everyone already has access
- Editing is a skill everyone already has
- Findability collapses past about thirty documents
- No structure means duplicates and contradictions
Learn more about The one you might not need to build
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2 Static site behind company sign-in
Documentation-shaped pages that only authenticated staff can fetch, with an owner and a review date per page.
- Structure, navigation, and search across everything
- Access follows the company directory
- The check must be enforced on a server, not just hidden
- Someone has to own it or it becomes a museum
Learn more about Static site with sign-in
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3 A hosted internal wiki
A wiki product. Honest answer for most companies under a certain size.
- Anyone can edit, search works, permissions built in
- No maintenance burden on anyone technical
- Per-seat pricing that grows with headcount
- Your content lives in their format
Learn more about The one you might not need to build
Sales pipeline
Who we are talking to, what stage they are at, what happens next.
What it is
A list of deals, each attached to a company and a person, moving through named stages, with notes and a next action and a date.
How you can build it
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1 A spreadsheet
One row per deal, columns for stage, value, owner, and next step. Under fifty deals this is genuinely fine.
- Working this afternoon, no cost, everyone can use it
- A month of it tells you exactly which fields matter
- No history, no reminders, no permissions
- Two people editing at once will lose something
Learn more about The one you might not need to build
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2 A hosted CRM
An off-the-shelf product built for this exact job.
- Email logging, reminders, and reporting included
- Nothing to maintain
- Per-seat pricing, and the cheap tier omits what you want
- You work the way the product thinks you should
Learn more about The one you might not need to build
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3 Your own database-backed board
Deals as records moving through named stages, with an activity history and exactly the fields your process needs.
- Fits your actual sales process rather than a generic one
- Integrates with whatever else you have built
- Weeks of work to reach what a CRM does on day one
- Adoption is the real problem, and software does not solve it
Learn more about Web application with a database
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4 Multi-tenant, if you sell it
The same product, but other companies use it too, with their data strictly separated.
- A pipeline tool becomes a business
- Roles, invitations, and billing become features
- One missed tenant check leaks a customer's deals to a rival
- Support and onboarding become permanent work
Learn more about Multi-tenant product
Applicant tracker
Applications in, candidates through stages, feedback in one place.
What it is
A system that receives applications, moves candidates through interview stages, collects structured feedback from interviewers, and tells everyone what is waiting on them.
How you can build it
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1 A form, a spreadsheet, and a shared folder
Applications land in a sheet; CVs land in a folder; interviewers comment in a document.
- Running in a day for a single role
- No cost, no procurement, no training
- Interviewers see each other's views before writing their own
- Personal data scattered with no retention policy
Learn more about The one you might not need to build
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2 A hosted hiring product
Built for this, including scheduling, scorecards, and compliance.
- Legal and retention obligations handled by people who study them
- Scheduling against real calendars, which is genuinely hard
- Expensive per role or per seat
- Rigid process that may not match yours
Learn more about The one you might not need to build
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3 Your own tracker
Candidates moving through stages, with feedback hidden until submitted.
- Independent feedback can be enforced, which improves hiring
- Fits an unusual process a product will not bend to
- Sensitive personal data becomes your legal responsibility
- Scheduling is a much bigger job than it looks
Learn more about Web application with a database
Inventory tracker
What we have, where it is, and who took it.
What it is
A record of items and their quantities across locations, updated as things are received, moved, used, or returned — usually with a barcode or a QR code in the loop.
How you can build it
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1 A spreadsheet with a count column
Current quantity per item, edited when things move.
- Immediate, free, and obvious to everyone
- Good enough for a stable cupboard of supplies
- Overwrites history — you never learn what happened
- Two people counting at once will disagree silently
Learn more about The one you might not need to build
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2 Movements in a database, count derived
Record every receipt, use, and return as a dated event; the current count is the sum.
- Full history, correction, and accountability for free
- Stock checks can record discrepancies instead of hiding them
- More to build than a quantity field
- Needs discipline to log movements as they happen
Learn more about Web application with a database
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3 Phone-first with barcode scanning
The camera reads the barcode and the item is found without typing, on the device already in the stockroom.
- Scanning is fast enough that people actually log movements
- Installs to a home screen with no app store
- Camera scanning is fiddly across devices
- Stockrooms have poor signal, which pushes you toward offline
Learn more about Installable web app (PWA)
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4 Offline-capable field app
Works fully in a basement or a van, syncing when it finds a network.
- Counts never lost to a dead signal
- The office sees the data as soon as the phone reconnects
- Conflicts when two people count the same shelf
- Substantially the hardest option here
Learn more about Mobile app that syncs with a web app
Invoice generator
Line items in, a clean PDF out, and a record of who has paid.
What it is
A tool that stores clients and rates, turns line items into a numbered invoice, produces a PDF, emails it, and tracks whether it has been paid.
How you can build it
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1 A template document
Duplicate last month's file, change the numbers, export a PDF.
- Zero setup, and totals you can see
- Fine at two invoices a month
- Sequential numbering depends on you remembering
- No record of what has been paid
Learn more about The one you might not need to build
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2 A browser tool that renders and prints
Enter line items, see a formatted invoice, print to PDF. Data stays on your machine.
- No server, no subscription, no data leaving the device
- Consistent formatting and arithmetic every time
- Clearing the browser loses your client list
- No chasing, no payment status
Learn more about App that runs entirely in the browser
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3 A database-backed app with payment status
Clients, rates, invoices, and whether each one has been paid.
- Knows what is overdue and can chase it
- Recurring invoices for retainers
- Money arithmetic and tax rules must be exactly right
- A sent invoice can never be silently edited
Learn more about Web application with a database
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4 Add a payment link to each invoice
Clients pay from the invoice, and the provider tells you when they have.
- Paid faster, and reconciliation is automatic
- Card details never touch your system
- A percentage of every invoice
- Webhooks arrive twice and out of order
Learn more about Application that moves money
Time tracker
Start, stop, and an honest answer about where the week went.
What it is
A timer attached to a project or task, storing intervals, and reporting totals by day, week, client, or tag.
How you can build it
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1 A notebook or a spreadsheet
Write down what you started and when you stopped.
- No tool to open, works in a meeting
- Forces you to notice where the time went
- Totals are manual arithmetic
- Easy to forget for a whole afternoon
Learn more about The one you might not need to build
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2 A browser tool storing locally
One start-stop button and a list of today's entries, kept in the browser.
- Free, private, and finished in a weekend
- No account, so no friction on the first use
- Laptop and phone become two separate trackers
- Clearing browser data loses everything
Learn more about App that runs entirely in the browser
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3 Synced across devices with an account
The same tool, but entries live on a server so any device sees them.
- Start on a phone, stop on a laptop
- Reports across months, and export for invoicing
- Accounts, hosting, and backups to run
- Sign-in friction on a tool used twenty times a day
Learn more about Web application with a database
Shift scheduler
Who is working when, who wants to swap, and who has not been told.
What it is
A rota for a team: shifts on a calendar, people assigned to them, availability and time-off recorded, and swap requests that need approval.
How you can build it
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1 A printed rota and a group chat
A shared sheet, printed and pinned up, with swaps negotiated in the chat.
- Everyone already knows how to use it
- No system to pay for or administer
- Swaps get agreed and then forgotten
- Nobody knows which version is current
Learn more about The one you might not need to build
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2 A web app with a personal view
Shifts on a grid, people assigned to them, and a page showing each person only their own.
- One published rota everyone reads the same way
- Availability and time off recorded properly
- Constraints conflict, and the app must explain rather than silently fail
- Publishing a change is a message to a person, not a database write
Learn more about Web application with a database
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3 Installable and phone-first
Staff add it to a home screen and check it between tasks; changes push a notification.
- Glanceable in seconds, which is how a rota is actually used
- No app store, so fixes ship the day they are written
- Notification support varies by platform
- Offline caching bugs show people last week's rota
Learn more about Installable web app (PWA)
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4 Sold to other businesses
Many venues on one deployment, each with their own staff and rules.
- A tool for one shop becomes a product
- Roles and billing become part of the offering
- Every query must be tenant-aware, forever
- Per-customer settings multiply what you must test
Learn more about Multi-tenant product
Internal admin panel
A safe window onto the production database for people who should not have one.
What it is
A private interface letting support and operations staff look up records, fix the common problems, and perform the handful of actions they otherwise ask an engineer for.
How you can build it
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1 Direct database access for the technical
Support asks an engineer, who runs a query.
- Nothing to build
- Fine while it happens twice a week
- Every request interrupts someone expensive
- One typo in a query changes the wrong rows
Learn more about The one you might not need to build
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2 An admin framework over the existing database
A generated interface for the tables, with the handful of actions support actually needs.
- Days of work for something used every day
- Removes a standing interruption permanently
- Generated interfaces expose more than they should by default
- Every action needs a permission, a confirmation, and an audit entry
Learn more about Web application with a database
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3 A separate service with a narrow API
The panel talks to a small set of deliberate operations rather than to the tables directly.
- Impossible to perform an operation nobody designed
- The same operations can back a chatbot or a script
- Every new capability is real work rather than a generated form
- More moving parts for a tool with ten users
Learn more about API or backend service
Live status dashboard
One screen on the wall that says whether things are fine.
What it is
A screen pulling the few numbers that matter — orders today, jobs queued, errors, deliveries late — from several systems and showing them large enough to read across a room.
How you can build it
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1 A shared chart in a spreadsheet
Paste in the exports, chart the columns, put it on the screen.
- Working today, and everybody can change it
- Proves which numbers people actually look at
- Somebody has to paste, forever
- Stale data looks exactly like fresh data
Learn more about The one you might not need to build
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2 Scheduled jobs into a store, charted
Jobs pull from each source on a timer; the page draws from what they collected and refreshes itself.
- Answers questions that span systems
- Every panel can show when it last succeeded
- Most of the work is cleaning data, not drawing charts
- A silently failing job makes the dashboard lie
Learn more about Data pipeline and dashboard
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3 Pushed live over an open connection
The server pushes changes as they happen instead of the page asking.
- Genuinely live for operational views where staleness is dangerous
- No polling load from a screen left on all day
- Costs scale with connected clients
- Reconnection and missed messages need real handling
Learn more about Real-time collaborative app
Automated reminders
The nudge that arrives without anyone remembering to send it.
What it is
A scheduled job that checks a condition — a date approaching, a form not filled in, a payment not made — and sends a message to the person who needs to act.
How you can build it
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1 Calendar invites and recurring events
Put the reminder in the calendar of the person who needs it.
- No code, and it already reaches everyone's phone
- Snoozing and dismissing already work
- Cannot depend on a condition — it fires regardless
- Someone must maintain the events by hand
Learn more about The one you might not need to build
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2 A scheduled job that emails or messages
A daily run reads the dates, works out what is due, and sends only what needs sending.
- A day of work removes a standing mental load
- Conditions can be as clever as you like
- Must record what it has sent, or retries double up
- Silent failure — nobody notices for a month
Learn more about Automation that runs without you
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3 Text messages people can reply to
The nudge arrives as a text, and the reply is captured as the response.
- Reaches people who never open email
- A reply can mark the thing done
- Per-message cost and opt-out obligations
- Handling unexpected replies is most of the work
Learn more about Conversational and text-based app
Email to anything
Forward a message; it becomes a task, a row, a note, or a calendar event.
What it is
An address that receives forwarded email, pulls out what matters, and files it somewhere useful — a task list, a spreadsheet, a notes system, a calendar.
How you can build it
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1 Provider rules and integrations
Your mail provider's filters plus an off-the-shelf automation service.
- Configured in twenty minutes with no code
- Reliable within its narrow abilities
- Cannot read a paragraph and pull the date out of it
- Breaks quietly when a template changes
Learn more about The one you might not need to build
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2 An inbound address feeding a small function
An email service posts each message to your code, which parses and files it.
- Any destination, any rule, entirely under your control
- Cheap to run — it only wakes when mail arrives
- Real email is quoted replies, signatures, and forwarded chains
- A silent parser failure loses things you believed captured
Learn more about Automation that runs without you
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3 A model extracts the fields
Instead of writing a parser, ask a model for the date, amount, and action.
- Handles messy prose no regular expression ever will
- New senders work without new rules
- Priced per message, and occasionally confidently wrong
- Needs a confirmation step for anything consequential
Learn more about AI-powered application
Price or availability watcher
Check a page on a schedule; tell me only when it changes.
What it is
A job that fetches a page or an API regularly, extracts one value — a price, a stock level, an appointment slot, a listing count — and notifies you when it moves past a threshold.
How you can build it
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1 A browser extension that flags the page
It notices the price while you are already on the site.
- No server, no schedule, no rate limits
- Sees exactly what you see, including logged-in prices
- Only works when you visit the page
- Breaks on every redesign
Learn more about Browser extension
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2 A scheduled job comparing against last time
Fetch, extract the number, compare, and only speak when it moved.
- Watches while you get on with your life
- History makes a chart possible later
- Sites restructure, render with JavaScript, and block bots
- Being a polite visitor is on you
Learn more about Automation that runs without you
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3 A command you run when you think of it
No schedule at all — just a command that prints the current number.
- An hour to write, nothing to deploy
- Nowhere to fail silently
- You have to remember to run it
- No notification, so no early warning
Learn more about Command-line tool
Research assistant
Give it a question; it reads a pile of sources and comes back with a summary and links.
What it is
A tool that takes a topic, gathers material from search results, feeds, or a folder of documents, and produces a structured summary with citations back to each source.
How you can build it
-
1 Paste sources in, summarise each, then combine
Fetch each URL, summarise it alone, then produce a combined answer with a link beside every claim.
- Cheaper and usually better than one enormous request
- Every claim traces to the source it came from
- Fetching pages is fragile and sometimes blocked
- Confident summaries of things a source did not say
Learn more about AI-powered application
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2 Index a corpus you already have
Point it at your own folder of papers or reports rather than the open web.
- No scraping, and the material is already trustworthy
- Answers stay inside a body you chose
- Extraction from PDFs is its own irritating problem
- Quality depends on retrieval, not on the model
Learn more about AI-powered application
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3 Run it on a schedule for a standing topic
A weekly job researches the same question and reports what changed.
- Turns a search habit into an arriving briefing
- Comparing against last week is where the value is
- Cost accrues whether or not anything changed
- Needs a store of what it already told you
Learn more about Automation that runs without you
Weekly digest
One message on Monday with everything you would otherwise check in six places.
What it is
A scheduled job that gathers the week's numbers and events from several systems and sends one readable summary — to you, a team, or a client.
How you can build it
-
1 Someone writes it on Monday
A person checks the sources and writes the summary.
- The commentary is better than any generated version
- Proves the digest is read before anything is built
- Half an hour of someone's week, every week
- Stops the moment they are on holiday
Learn more about The one you might not need to build
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2 A scheduled job that assembles and sends
Pull the numbers, compare against last week, and send one readable summary.
- Arrives rather than waiting to be opened
- A fraction of the work of building a dashboard
- A failed source must be reported, not reported as zero
- The comparison sentence is the part that needs care
Learn more about Automation that runs without you
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3 Built on a store the dashboards share
The digest reads the same collected data as the charts, so they can never disagree.
- One pipeline serving both a screen and an inbox
- Trends over months come free
- A pipeline to build before the first digest sends
- Overkill if three numbers were the whole ask
Learn more about Data pipeline and dashboard
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4 A command you run before the meeting
Same gathering logic, invoked by hand and pasted where it is needed.
- An afternoon, and no scheduling infrastructure
- Nothing to fail silently at 3am
- Only happens when someone remembers
- No archive unless you keep the output
Learn more about Command-line tool
Form to workflow router
A submission arrives and the right things happen, in the right order, to the right people.
What it is
A small system sitting behind a form — a request, a report, an application — that files the submission, notifies whoever owns it, and tracks it until it is resolved.
How you can build it
-
1 A shared inbox and a rota
Submissions land in one mailbox; whoever is on duty handles them.
- Works from day one with no software
- Exposes what the real categories are
- No status, so nothing is ever provably finished
- Things fall through when everyone assumes someone else has it
Learn more about The one you might not need to build
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2 A job that posts each submission to the right place
Store it, then notify the owning channel with a link and a button to mark it done.
- A few days of work turns an inbox into a process
- Routing rules can live as editable data, not code
- Needs a default destination or unmatched submissions vanish
- Chat notifications get muted and then ignored
Learn more about Automation that runs without you
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3 A tracker with status and targets
Each submission is a record moving through states, with response-time targets and escalation.
- Submitters can check their own status
- Volume and resolution time become reportable
- A real application to run, not a script
- Process discipline it enforces may be resented
Learn more about Web application with a database
Two-way marketplace
Buyers on one side, sellers on the other, and a cold-start problem in the middle.
What it is
A platform where one group lists something — goods, services, time, space — another group buys it, and the platform handles discovery, the transaction, and the money moving between them.
How you can build it
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1 Introductions made by hand
A form on each side and you personally matching them, in a spreadsheet.
- Tests the market before building any of it
- You learn exactly where the friction is
- Does not scale past a few dozen matches
- Feels unimpressive even when it is working
Learn more about The one you might not need to build
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2 A listings site with contact details
Sellers list, buyers browse and get in touch. The platform does not handle the transaction.
- Much simpler than handling money
- Enough to prove people want to find each other
- Both sides transact privately and you learn nothing
- No leverage to add trust or guarantees
Learn more about Web application with a database
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3 Payments and payouts through the platform
Funds are held until delivery is confirmed, and the platform takes a cut.
- Payment protection is a real reason not to go around you
- A revenue model that scales with the market
- Refunds, disputes, and payouts are relentless edge cases
- Regulatory obligations arrive with holding other people's money
Learn more about Application that moves money
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4 An API for partners
Supply-side partners push inventory in programmatically instead of typing it.
- Solves the cold-start problem on one side at a stroke
- Partners become invested in the platform working
- Once someone integrates, you cannot freely change anything
- Documentation and versioning become permanent work
Learn more about API or backend service
Community forum or local board
Posts, replies, and the slow realisation that moderation is the product.
What it is
A space where members post, reply, and vote — a neighbourhood board, a hobby community, a customer forum — with accounts, categories, and moderation.
How you can build it
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1 A group chat
A chat platform with channels. Most communities should start here.
- Instant, free, and where people already are
- Conversation feels alive from the first day
- Nothing is findable a week later
- Not indexed, so the community cannot be discovered
Learn more about The one you might not need to build
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2 Hosted forum software
Mature forum products exist and have solved moderation and spam.
- Trust levels, flagging, and spam handling out of the box
- Searchable, public, and good for discovery
- Hosting cost or self-hosting effort
- Heavy for a community of thirty people
Learn more about The one you might not need to build
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3 Your own posts-and-replies app
Accounts, threads, and categories, built to fit one specific community.
- Shaped exactly around how this group works
- Threading is a satisfying data-modelling problem
- Spam arrives within days of going public
- Moderation is the product and it is never finished
Learn more about Web application with a database
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4 Live updating threads
Replies appear without a refresh, and you can see who is typing.
- An active thread feels like a room rather than a page
- Removes the refresh habit entirely
- Open connections cost money per reader
- Considerable complexity for a marginal feel
Learn more about Real-time collaborative app
Event RSVP and ticketing
A date, a capacity, a list of names, and possibly money.
What it is
A page describing an event with a way to register, a cap on numbers, a confirmation, and a list at the door — free or paid.
How you can build it
-
1 A page and a hosted form
Details on a static page, replies into a form service, capacity managed by you closing the form.
- Free, and live in an hour
- Guests need no account
- Capacity is honour-system until you notice
- No tickets, no check-in
Learn more about Static site that buys its backend
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2 An event ticketing platform
A product that already handles capacity, payment, refunds, and check-in.
- Everything hard is already solved and tested
- Discovery through their audience
- A per-ticket fee and their branding
- Attendee data is theirs as much as yours
Learn more about The one you might not need to build
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3 Your own registration app
Registrations as records with a hard capacity enforced in the database.
- Waitlists that promote automatically
- Attendee data and communications entirely yours
- Two people buying the last seat is a genuine concurrency problem
- Support on the day becomes your job
Learn more about Web application with a database
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4 Paid tickets end to end
Checkout, refunds, transfers, and a QR code for the door.
- Money and capacity settled in one transaction
- Check-in becomes a scan rather than a list
- Refund and transfer policy must be decided before selling one ticket
- Failed payments and disputes need handling
Learn more about Application that moves money
Shared cost splitter
Who paid for what on the trip, and who owes whom at the end.
What it is
A shared record of expenses within a group — a holiday, a house, a dinner — that works out the smallest set of payments to settle everything.
How you can build it
-
1 A shared spreadsheet
One row per expense, a formula for the balances.
- Everyone can see and check the maths
- Working before the trip starts
- Settling up is manual arithmetic
- Uneven splits get fudged
Learn more about The one you might not need to build
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2 A browser app storing locally
Add people and expenses, see balances and the smallest set of payments to settle.
- The settle-up algorithm is genuinely satisfying to write
- No accounts, no server, no cost
- Only the person holding the device has the data
- Rounding a pound three ways needs a deliberate rule
Learn more about App that runs entirely in the browser
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3 Shared by link with a server
A group has a URL; anyone with it can add expenses and see the same balances.
- Everyone enters their own spending as it happens
- Receipts and multiple currencies become possible
- A link is the only security, so it must be unguessable
- Now you are storing other people's financial detail
Learn more about Web application with a database
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4 Installable for a trip
Home-screen icon, works with patchy signal abroad.
- Usable on a mountain with no data
- No app store between you and the trip
- Offline entries from several people need reconciling
- Cached versions get stale mid-trip
Learn more about Installable web app (PWA)
Volunteer or shift signup
Slots that need filling, and people claiming them without anyone coordinating by email.
What it is
A published list of slots — times, roles, tasks — where people can claim one, see what is left, and be reminded before it happens.
How you can build it
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1 A sign-up sheet, paper or shared
A physical sheet, or a shared document anyone can type into.
- No barrier at all — people sign up in seconds
- Zero cost and zero setup
- Only one place, and it can be lost or overwritten
- No reminders, so no-shows are common
Learn more about The one you might not need to build
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2 A page of slots with a claim button
Public list, claim with a name and an email, no account required.
- Everyone sees what is still empty, which drives signups
- Reminders the day before cut no-shows sharply
- Two people claiming the last slot at once needs handling
- Someone must run it between events
Learn more about Web application with a database
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3 A form and an automated confirmation
A hosted form writes to a sheet; a job sends the confirmation and the reminder.
- Almost nothing to build, and reminders still happen
- Organiser gets a printable list for free
- Remaining capacity is not visible to volunteers
- Two services to keep configured
Learn more about Static site that buys its backend
Neighbourhood tool library
Who owns the ladder, who has it now, and when it is coming back.
What it is
A shared catalogue of items a group is willing to lend, with a way to ask to borrow, a record of who currently has what, and a due date.
How you can build it
-
1 A group chat and trust
Ask the street whether anyone has a ladder.
- Already works, already exists, no setup
- The social bond is the point, not the software
- Nobody knows what exists until they ask
- No memory of who has what
Learn more about The one you might not need to build
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2 A shared catalogue with status
Items with an owner and a state — available, requested, out, overdue.
- A small, complete state machine you can finish
- Ownership and due dates become visible facts
- Deposits, damage, and disputes are social, not technical
- Nagging notifications lose you members
Learn more about Web application with a database
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3 Phone-first and installable
Photograph an item to list it, claim from a phone in a shed.
- Listing something takes under a minute
- Home-screen presence keeps it in mind
- Photo storage costs grow quietly
- Push notifications differ by platform
Learn more about Installable web app (PWA)
Run tracker
A line on a map, a pace, and a history that makes you want to go again.
What it is
A phone app that records location while you run, works out distance, pace, and elevation, then stores the run and shows progress over weeks.
How you can build it
-
1 Log runs by hand afterwards
Type in distance and time when you get home; the app does the pace and the totals.
- A weekend to build, and no sensors involved
- Works with a treadmill or a track, where GPS is useless
- No route, no splits, no elevation
- Depends on you remembering
Learn more about App that runs entirely in the browser
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2 Record GPS in the browser
An installable page that reads location while you run and stores the track locally.
- No app store, and updates ship immediately
- Enough for distance and pace on most phones
- Background recording with the screen off is unreliable
- Battery use is hard to control from a browser
Learn more about Installable web app (PWA)
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3 A native mobile app
Proper background location, notifications, and audio cues, installed from the store.
- Keeps recording with the screen locked, which is the whole job
- Access to heart-rate straps and watch sensors
- Store review, signing, and annual fees
- Raw GPS is noisy and needs real smoothing work
Learn more about Mobile application
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4 Phone records, web app analyses
The run is captured offline on the phone and synced to a bigger screen for the history and the charts.
- Right tool for each half — capture in the field, analysis at a desk
- Runs survive a phone being lost
- Two schemas to keep in step
- Sync conflicts from an edit in both places
Learn more about Mobile app that syncs with a web app
Trail mapping with offline access
Maps, position, and notes where there is no signal at all.
What it is
An app carrying downloaded map tiles and trail data so it can show where you are, record a track, and capture waypoints and photos entirely without a network — syncing when you are back in coverage.
How you can build it
-
1 Download maps in an existing app
Established outdoor apps already cache regions offline.
- Reliable, tested by people whose safety depended on it
- Nothing to build
- You cannot add the fields your survey or club needs
- Subscription, and their choice of map data
Learn more about The one you might not need to build
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2 Cached tiles in an installable web app
Pre-download a region's tiles into browser storage and show position from the browser location API.
- No app store, and one codebase for phone and desktop
- Enough for a known area with a modest tile set
- Browser storage limits are real and vary by device
- Background tracking is weak compared to native
Learn more about Installable web app (PWA)
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3 A native app with managed offline regions
The user chooses regions to download; tracks and waypoints are stored on the device.
- Reliable positioning and storage for a full day out
- Camera and compass available for waypoints
- Map tiles are large and region management is fiddly
- Must be tested in airplane mode, up a hill
Learn more about Mobile application
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4 Two-way sync with a web app
Field captures sync up when signal returns, and route plans sync down before you leave.
- The office sees the survey without anyone exporting anything
- Plans prepared at a desk reach the phone automatically
- Conflict rules must be decided before any sync code is written
- Bugs appear only in sequences that are miserable to reproduce
Learn more about Mobile app that syncs with a web app
Habit tracker
A grid of squares you fill in, and a streak you do not want to break.
What it is
A list of things you intend to do regularly and a calendar grid showing which days you did, with streaks and totals.
How you can build it
-
1 A paper calendar and a pen
Cross off the day. The original, and still excellent.
- Zero friction, always visible, never needs charging
- Nothing to lose to a cleared browser
- No totals, no streak count, no history you can search
- Only in one place
Learn more about The one you might not need to build
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2 A browser app storing locally
Tap today's square; see the last thirty days as a grid.
- Finishable in a weekend, and genuinely used daily
- Private by construction — nothing leaves the device
- Clearing browser data ends a hundred-day streak
- Phone and laptop are two separate trackers
Learn more about App that runs entirely in the browser
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3 Installable with a daily reminder
Home-screen icon and a notification at the hour you choose.
- The reminder is what makes a tracker work at all
- Still no app store, still free
- Notification support and reliability vary by platform
- Service worker caching bugs serve stale versions
Learn more about Installable web app (PWA)
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4 Account-backed and synced
Entries on a server so any device sees the same streak.
- Nothing is lost with a device
- Long-term history and comparison across months
- Sign-in friction on a tool used for two seconds a day
- Running costs for something with one user
Learn more about Web application with a database
Recipe and food tracker
What we cook, what we need to buy, and what we actually ate.
What it is
A store of recipes with ingredients and steps, a weekly meal plan built from them, and a shopping list generated by combining what the plan needs.
How you can build it
-
1 A notes app and a shopping list app
Recipes as notes, list written by hand each week.
- Already on every phone in the house
- No structure to design
- The list is assembled by hand every single week
- Quantities across recipes never get combined
Learn more about The one you might not need to build
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2 Recipes as content, list generated
Structured ingredients in a CMS, with the weekly plan producing a combined list.
- Generating the list is the satisfying part, and it works
- Recipes become a nice public site if you want one
- Units are the real problem and need a structured model
- A build step between editing and seeing it
Learn more about Static site with a CMS
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3 A web app with a plan and a pantry
Drag recipes onto days; the list subtracts what you already have.
- Handles the whole weekly loop, not just the recipes
- Several people in the house can add to it
- Pantry state goes stale unless someone maintains it
- A real app to run for a household of four
Learn more about Web application with a database
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4 Installable, kitchen-friendly
Big type, screen kept awake, works while cooking with greasy hands.
- Cooking mode is where this idea is actually used
- Shopping list works in a shop with poor signal
- Offline edits from two people need reconciling
- Keeping the screen awake drains the battery
Learn more about Installable web app (PWA)
Family chores and allowance
Tasks, ticks, and a running total the children check more often than you do.
What it is
A shared board of household tasks with points or money attached, claimed and completed by family members, with a balance per person and a payout day.
How you can build it
-
1 A chart on the fridge
Stickers, a marker, and a weekly payout.
- Visible to everyone all the time, which is the whole mechanism
- Impossible to break or forget the password to
- Totals are mental arithmetic and get disputed
- No history beyond this week
Learn more about The one you might not need to build
-
2 A shared browser page on the family tablet
Tasks with values, a tick per person, a running total, stored on the device.
- No accounts for children, no data leaving the house
- A weekend to build and immediately used
- One device only, and clearing it loses balances
- No approval step, so disputes stay disputes
Learn more about App that runs entirely in the browser
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3 Accounts with a parent approval step
Children claim, a parent approves, and the history settles arguments.
- Approval and history are what make it fair
- Works from each person's own phone
- Children's data deserves genuine care
- Sign-in friction for a nine-year-old is real
Learn more about Web application with a database
Plant care reminders
Which plant, how often, when last — and a nudge on the right day.
What it is
A list of plants with a watering interval and a last-watered date, sending a reminder when one is due and recording the care as it happens.
How you can build it
-
1 Recurring calendar events
A repeating event per plant.
- Nothing to build, reminders already reach your phone
- Snoozing already works
- Fixed schedule that ignores when you actually watered
- Editing twenty events by season is miserable
Learn more about The one you might not need to build
-
2 A scheduled job that emails what is due
A list of plants and intervals in a file; a daily job sends one summary of what needs water.
- A day to build, and the interval follows the last watering
- One daily digest rather than eight separate alerts
- Marking something watered means editing the file
- No photos, no history
Learn more about Automation that runs without you
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3 An installable app with notifications
Add a plant with a photo, tap watered, get a nudge when due.
- Logging is two taps, which is why it keeps happening
- Photo history shows whether a plant is actually improving
- Notification reliability varies by platform
- Photo storage grows quietly
Learn more about Installable web app (PWA)
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4 A native app with proper reminders
Local notifications that fire reliably, and a widget on the home screen.
- Reminders that genuinely arrive, which is the product
- Camera integration is smoother
- Store review and fees for a personal utility
- Two platforms for a small idea
Learn more about Mobile application
Reading and watching list
What to read next, what you finished, and what you thought of it.
What it is
A personal catalogue of books, films, or shows with a status — want, in progress, finished — plus ratings, notes, and dates.
How you can build it
-
1 A list in a notes app
A running list of what to read next and what you finished.
- Already synced across your devices
- No structure to maintain
- No ratings, dates, or filtering
- Becomes an unreadable wall after a year
Learn more about The one you might not need to build
-
2 A browser app with local storage
Titles with a status and a rating, filtered by state.
- A clean list-and-detail app finishable in a weekend
- Private, free, and offline
- One device, and clearing the browser loses it
- Covers and metadata typed by hand
Learn more about App that runs entirely in the browser
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3 Pull metadata from a public catalogue
Search a title, get the cover and details, store your own status against it.
- Entry becomes a search rather than typing
- A public year-in-review page becomes possible
- Editions and adaptations make identity fuzzy
- Rate limits and terms mean you must cache what you fetch
Learn more about Web application with a database
On-this-day photo app
A quiet daily reminder of what you were doing a year ago.
What it is
Something that looks through your own photo library for pictures taken on today's date in previous years and shows them, or sends one to you each morning.
How you can build it
-
1 A script over a folder
Read the dates on your files and print or open everything from this day in past years.
- An hour to write, and it works on the photos you already have
- Nothing uploaded anywhere
- You have to remember to run it
- No notification, so it is not really a daily thing
Learn more about Command-line tool
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2 A scheduled job that emails you one
The same logic on a timer, sending a single picture each morning.
- Arrives without being asked, which is the whole appeal
- Cheap and simple to run
- Photos must live somewhere the job can reach
- Email is a poor frame for a photograph
Learn more about Automation that runs without you
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3 A browser app over a chosen folder
Point the page at a local folder; nothing is uploaded.
- Photographs never leave the machine
- Good enough for a weekly browse
- Browser file access is clunky and permission-gated
- No notification
Learn more about App that runs entirely in the browser
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4 A native app reading the photo library
Proper access to the phone's library, with a morning notification.
- The photos are already there, with dates and places
- Notifications make it a daily ritual
- Photo library access is sensitive and rightly gated
- Metadata is inconsistent, wrong, or missing
Learn more about Mobile application
Fantasy sports application
A league, a draft, weekly scoring, and a group chat that never shuts up.
What it is
A private league where members pick real players, points are computed from real-world performances each week, and standings update through a season.
How you can build it
-
1 A spreadsheet and a group chat
Rosters in a sheet, scores entered weekly, standings shared in the chat.
- The league runs this season, not next
- Arguments are settled by looking at the sheet together
- Someone spends an hour every week
- Draft day is chaos
Learn more about The one you might not need to build
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2 A web app scoring from an imported stats file
Rosters as records; a weekly import feeds the scoring rules and the standings.
- Scoring becomes automatic and consistent
- History and reporting across a season
- Statistics arrive late and get corrected retroactively
- A correction after publishing means recomputing history
Learn more about Web application with a database
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3 Automate the weekly cycle
A job pulls the stats, recomputes, and posts the results to the league chat.
- The commissioner stops being a job
- Everyone hears the results at the same moment
- Silent failure on a Sunday night is very visible on Monday
- Depends on somebody else's data feed staying stable
Learn more about Automation that runs without you
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4 A live draft room
Everyone in at once, a pick timer, and the board updating for all of them.
- Draft day is the event the whole season hangs on
- No refreshing, no arguments about who picked first
- Your only real load test, with everyone arriving at once
- Reconnection handling is essential, not optional
Learn more about Real-time collaborative app
Pickup game finder
Six people want to play, one court is free, and nobody wants to organise it.
What it is
A place to post a game — sport, place, time, players needed — and for others to join, with a minimum number below which it is cancelled.
How you can build it
-
1 A recurring group chat message
Someone posts "football, Thursday, 7pm" and counts the thumbs up.
- Already works, in the place people already are
- No adoption problem whatsoever
- Reactions are not commitments
- Nothing visible to anyone outside the chat
Learn more about The one you might not need to build
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2 A web app with a minimum player count
Post a game with a time, a place, and a minimum; it is on only if enough people commit.
- The minimum turns a vague thread into a decision
- New people can find games without knowing anyone
- Needs local density to be useful at all
- Joining is still not turning up
Learn more about Web application with a database
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3 Installable with local notifications
Regulars are told when a game near them is posted, from a home-screen icon.
- Notifications are what fill a game at short notice
- No app store between an idea and a Thursday
- Location permissions put people off
- Notification reliability varies
Learn more about Installable web app (PWA)
Text-message survey
One question by SMS, a reply back, and a response rate a web form will never touch.
What it is
A system that texts people a question, records their replies, and can ask a follow-up — for check-ins, feedback, field data collection, or research.
How you can build it
-
1 A link to a web form
Text people a link to a hosted form.
- Nothing to build, and rich question types
- Free at small volumes
- Response rates collapse compared to replying in the thread
- Useless to anyone on a poor connection
Learn more about Static site that buys its backend
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2 One question by SMS, replies captured
A messaging provider sends the question and posts each reply to your code.
- Response rates a web form will never reach
- No app, no login, no data plan required
- Consent, opt-out, and sender registration are legal obligations
- Per-message cost on both directions
Learn more about Conversational and text-based app
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3 Branching follow-up questions
The answer decides the next question, with each person's position tracked.
- Much richer data than a single question
- Feels like a conversation rather than a form
- Conversation state is the hard part — people reply days later
- Every unexpected reply needs a graceful answer
Learn more about Conversational and text-based app
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4 A model interprets free-text replies
Let people answer in their own words and classify the responses afterwards.
- No forcing real answers into five radio buttons
- Themes emerge that you did not think to ask about
- Classification is confidently wrong sometimes
- Costs scale with responses
Learn more about AI-powered application
Team standup bot
It asks everyone three questions and posts the summary. No meeting required.
What it is
A chat bot that messages each team member on a schedule, collects short answers, and posts a collated summary to a shared channel.
How you can build it
-
1 A recurring reminder in the channel
A scheduled message asking everyone to post their update in a thread.
- Configured in a minute with no code
- Removes the meeting immediately, which is the actual goal
- No collation — the thread is as messy as the meeting was
- Nothing to report on
Learn more about The one you might not need to build
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2 A bot that asks each person and collates
Direct messages at a set time, replies gathered, one summary posted to the channel.
- Answering privately is faster and less performative
- The summary is genuinely readable
- Time zones and partial responses need deciding
- Highlighting who did not answer turns it hostile
Learn more about Conversational and text-based app
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3 A scheduled job with no chat integration
Emails the questions and posts a digest, if your team does not live in a chat tool.
- Works with any team, no platform dependency
- Simpler to build than a chat integration
- Email is a slower loop than chat
- Nobody reads the digest where they are already working
Learn more about Automation that runs without you
Personal finance dashboard
Every account in one picture, and an honest answer about the month.
What it is
A tool that imports transactions from bank exports, categorises them, and shows spending by category, income against outgoings, and trends over months.
How you can build it
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1 A spreadsheet with a pivot table
Paste the bank export in, categorise with a lookup column, pivot by month.
- An afternoon, and the maths is visible and checkable
- Nothing sensitive leaves your machine
- Pasting and categorising is a monthly chore
- Charts are as good as your patience
Learn more about The one you might not need to build
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2 A browser app that never uploads
Drop the CSV onto a page that parses, categorises, and charts entirely in the browser.
- Your most sensitive data is structurally never transmitted
- Rules and corrections persist between visits
- Rules live on one device
- Still a manual export from each bank
Learn more about App that runs entirely in the browser
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3 A pipeline with an account aggregator
A service pulls transactions automatically into a store you chart from.
- No exporting — it is simply up to date
- Multi-account net worth becomes possible
- Handing bank credentials to an aggregator, and paying monthly
- Now you are storing your own financial history on a server
Learn more about Data pipeline and dashboard
Ask questions of your own documents
Point it at a folder of PDFs and get answers with citations.
What it is
A tool that indexes a body of your own material — contracts, manuals, research, meeting notes — and answers questions about it by finding the relevant passages and summarising them with references back.
How you can build it
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1 Full-text search over the folder
Index the documents and search them. Not an answer, but often what you needed.
- Fast, free, deterministic, and never invents anything
- An afternoon of work
- Only finds the words you typed
- No synthesis across documents
Learn more about Command-line tool
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2 Retrieve passages, then summarise
Split documents into passages, find the closest ones to the question, and answer using only those, with citations.
- Answers questions phrased differently from the text
- Every claim traces to a passage you can check
- Quality is decided by retrieval, not by the model
- Priced per question, and it must say when it does not know
Learn more about AI-powered application
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3 Entirely in the browser
Parse and index locally, sending only the retrieved passages anywhere.
- Confidential documents never leave the machine wholesale
- No server to run or secure
- Indexing large corpora in a browser is slow
- Index rebuilt per device
Learn more about App that runs entirely in the browser
Flashcards with spaced repetition
The card comes back exactly when you were about to forget it.
What it is
Decks of question-and-answer cards, reviewed daily, where each answer's difficulty decides how many days pass before that card appears again.
How you can build it
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1 Paper cards
Index cards and three boxes for daily, weekly, and monthly.
- The scheduling idea works perfectly well in cardboard
- Writing a card by hand is itself good for recall
- No statistics, and no cards on a bus
- Scheduling by hand gets sloppy
Learn more about The one you might not need to build
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2 An existing spaced-repetition app
Mature tools exist with tuned algorithms and shared decks.
- The algorithm is better than the one you would write
- Thousands of ready-made decks
- Interfaces are famously unfriendly
- Your cards live in their format
Learn more about The one you might not need to build
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3 A browser app storing locally
Create cards, review what is due, and let the answer decide the next interval.
- A real algorithm at the centre of a weekend project
- Works offline, costs nothing, shares nothing
- Decks trapped on one device without an export
- A missed week creates a backlog that ends the habit
Learn more about App that runs entirely in the browser
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4 Installable and synced
Home-screen icon, daily reminder, and decks that follow you between devices.
- Reviewing on a phone in a queue is when this actually happens
- Streaks survive a lost laptop
- Sync means accounts, a server, and running costs
- Notification reliability varies by platform
Learn more about Installable web app (PWA)
Interview or language practice
A patient partner who asks questions, listens, and tells you how it went.
What it is
A tool that runs a practice conversation — job interview questions, a language exchange, a sales pitch — and afterwards gives specific feedback on the answers.
How you can build it
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1 A list of questions and a timer
A page of good questions, one at a time, with somewhere to type an answer.
- Most of the benefit is answering out loud, which needs no software
- Free, instant, and honest about what it is
- No feedback at all
- Easy to skip the hard questions
Learn more about Very simple static website
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2 A model gives specific feedback
Answer in text; get feedback against stated criteria that quotes your own words back.
- Unlimited patience and no social cost
- Feedback can be tailored to a pasted job description
- Generic encouragement is worthless, so the prompt must carry criteria
- It cannot know what a particular company wants
Learn more about AI-powered application
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3 Spoken, in real time
Speech in and out, so the pacing and the pauses are realistic.
- Practises the actual skill, which is talking
- Hesitation and filler become visible
- Latency breaks the illusion quickly
- Costs per minute, in both directions
Learn more about Conversational and text-based app
Converter or calculator tool
Numbers in, numbers out. The smallest complete application there is.
What it is
A single-purpose tool that transforms input into output — units, currency, timezones, mortgage payments, cooking quantities, colour formats.
How you can build it
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1 A single static page with a script
Two fields and a formula, converting as you type.
- An hour of work, free hosting, bookmarkable
- Loads instantly and works offline once cached
- Anything rate-based goes stale without a source and a date
- No history unless you add storage
Learn more about App that runs entirely in the browser
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2 Values encoded in the URL
The conversion lives in the address, so a result can be shared or bookmarked.
- Sharing a specific conversion becomes possible
- Still no server, still one file
- URL parsing is a small amount of extra care
- Not obvious to users unless you show it
Learn more about Very simple static website
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3 Rates refreshed on a schedule
For currency or tax, a job fetches the rates daily and commits them into the site.
- Accurate without a server at request time
- The date the rates were fetched can be shown honestly
- A pipeline that can silently stop
- Depends on a rates provider and its terms
Learn more about Automation that runs without you
Daily puzzle or word game
One puzzle a day, the same for everyone, shareable without spoilers.
What it is
A small browser game with a single daily puzzle, a handful of attempts, a streak, and a spoiler-free result people can paste into a chat.
How you can build it
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1 Puzzle chosen from a list by today's date
All the puzzles ship with the page; the date picks which one, and progress is kept in the browser.
- No server at all, so it survives any amount of traffic for free
- Everyone worldwide gets the same puzzle without coordination
- The answers are in the page source for anyone curious
- Puzzles run out unless you generate them
Learn more about App that runs entirely in the browser
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2 Puzzles fetched from a small endpoint
The page asks for today's puzzle, so the answer is not shipped in advance.
- Puzzles can be added without redeploying
- Answers stay server-side until needed
- Now there is a server that can go down on launch day
- Costs scale with the audience you were hoping for
Learn more about API or backend service
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3 Accounts, streaks, and leaderboards
Results stored per player, with friend leaderboards and a puzzle archive.
- Streaks and rivalry are what make a daily game stick
- Real data on which puzzles are too hard
- Accounts are friction on something people play for two minutes
- Cheating becomes worth someone's time
Learn more about Web application with a database
Multiplayer trivia or quiz
Everyone answers on their phone, the answers appear on the big screen.
What it is
A host screen showing a question and a countdown, with every player answering on their own phone by joining a room code — scores updating live between rounds.
How you can build it
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1 A slide deck and shouting
Questions on a screen, answers on paper, one person marking.
- Works tonight, and the fun is mostly social anyway
- No devices to fail in a pub with no signal
- Marking is slow and error-prone
- No pace, and no scores between rounds
Learn more about The one you might not need to build
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2 Polling, refreshed
Players answer on their phones; the host screen asks the server for results every second or two.
- Much simpler than open connections, and often indistinguishable
- Ordinary hosting handles it
- Polling load grows with players
- Timing feels slightly loose
Learn more about Web application with a database
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3 Pushed live over an open connection
A room code, players joining, and questions pushed to everyone at once.
- The room reacting together is the entire product
- Scores can update between rounds without a refresh
- Late joiners, locked phones, and drops all need defined outcomes
- Score against server receipt time, or the fastest network wins
Learn more about Real-time collaborative app
Generative art or drawing tool
Rules and randomness in, something worth printing out.
What it is
A browser tool that draws — from parameters you tweak, from randomness, or from your mouse — with controls to explore variations and a way to export the result.
How you can build it
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1 A script that writes an image file
Run it, get a PNG. No interface at all.
- Straight to the interesting part with no interface work
- Easy to render at print resolution
- No live tweaking, so exploration is slow
- Only you can use it
Learn more about Command-line tool
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2 A canvas with sliders in the browser
Live preview, a few controls, a randomise button, and save as an image.
- The immediate feedback loop is the whole pleasure
- Free to host and shareable as a link
- High resolution can lock up a phone
- Export needs a separate, slower path from the preview
Learn more about App that runs entirely in the browser
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3 Parameters encoded in the URL
A seed and the settings live in the address, so a piece someone loves can be returned to.
- Reproducibility, which is what makes it feel like a tool
- Sharing a specific piece costs nothing
- Changing the algorithm invalidates old links
- URL length gets awkward with many parameters
Learn more about Very simple static website
Music or skill practice tracker
What you practised, for how long, and the recording from six months ago.
What it is
A log of practice sessions — pieces or exercises, duration, notes, tempo — and optionally short recordings, so progress is visible over months.
How you can build it
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1 A practice diary
A notebook by the instrument.
- Zero friction at the moment you sit down
- Notes in the margin are better than any form field
- No totals across months
- No recordings to compare against
Learn more about The one you might not need to build
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2 A browser timer with local storage
Start a session, pick what you are working on, stop, add a note.
- Two taps to start, which is the only thing that matters
- Weekly totals make invisible progress visible
- One device, and no recordings
- Lost with the browser data
Learn more about App that runs entirely in the browser
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3 Installable, with recording
Record short clips in the browser and play them back months later.
- Hearing last spring is the most motivating feature there is
- Home-screen icon keeps it in the routine
- Audio files are far larger than anything else in the app
- Browser recording support and formats vary
Learn more about Installable web app (PWA)
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4 Synced with a server
Sessions and recordings stored centrally, available anywhere, shareable with a teacher.
- A teacher can listen between lessons
- Nothing lost with a device
- Audio storage costs grow steadily
- Accounts and privacy for what may be a child's practice
Learn more about Web application with a database
Smart home dashboard
One screen for lights, heating, and sensors from four brands that ignore each other.
What it is
A local dashboard and automation layer over the devices already in a house — showing state, offering controls, and running rules the vendor apps cannot express.
How you can build it
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1 The vendor apps you already have
Four apps, one per brand, and their own scenes and schedules.
- Nothing to build or maintain
- Vendor support when a device misbehaves
- No rule can span two brands, which is the whole frustration
- Everything routes through their cloud
Learn more about The one you might not need to build
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2 An off-the-shelf home automation hub
A hub product on a small computer at home, with integrations already written for most devices.
- Cross-brand automations, locally, without the vendor cloud
- Someone else maintains the hard integration code
- A box in the house that you now own the uptime of
- Its configuration language is a thing to learn
Learn more about App that talks to hardware
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3 Your own dashboard over the hub
Let the hub talk to devices; build the screen and the rules you actually want on top of it.
- Exactly the view your household needs, not a generic one
- History and charts stored the way you want them
- Another layer to keep working across hub updates
- Tempting to rebuild what the hub already does
Learn more about Web application with a database
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4 A wall display that shows the state
A tablet or panel in the hallway showing what matters, with a few controls.
- Glanceable by everyone, including guests
- Removes the phone from a light switch
- A screen always on is a real power and lifespan question
- Touch targets and always-on layout are their own design job
Learn more about App that talks to hardware
Environment sensor logger
Temperature, humidity, or soil moisture, every five minutes, for a year.
What it is
A small battery or mains powered device reading a sensor at intervals and reporting the values somewhere they can be charted — a greenhouse, a room, a fridge, a beehive.
How you can build it
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1 An off-the-shelf sensor and its app
A commercial thermometer that logs to a phone.
- Working the day it arrives
- Calibrated and weatherproofed by someone else
- Data locked in their app, often behind a subscription
- No control over interval or what is measured
Learn more about The one you might not need to build
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2 A dev board printing over a cable
A microcontroller with one sensor, logging over serial to a laptop.
- The fastest route to a working reading, and easy to debug
- Parts cost very little
- Tethered to a computer, so not really deployed
- Nothing is stored unless the laptop is running
Learn more about Firmware and embedded software
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3 Wireless reporting to a small server
The device reports readings over wifi to something at home that stores them.
- Runs unattended for months
- Charts and thresholds become possible
- Deep sleep and power budgeting become the real engineering
- Devices reset and lose hours of data
Learn more about App that talks to hardware
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4 Charted and alerting
Readings feed a store that draws the trend and shouts when something crosses a line.
- A year of data is where the insight actually is
- Alerts turn a log into something useful
- Gaps in the data must be handled honestly rather than smoothed away
- A pipeline to keep running for a hobby sensor
Learn more about Data pipeline and dashboard
Bike computer or GPS logger
A device you built, on the handlebars, showing speed and recording the ride.
What it is
A self-contained device with a GPS module and a small display that shows speed and distance while riding and stores the track for later.
How you can build it
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1 Use the phone already in your pocket
A phone has GPS, a screen, and a battery. Mount it and be done.
- No hardware to design, buy, or waterproof
- Sensors and maps already there
- A phone on handlebars in the rain is a bad idea
- Not the project if building the device is the point
Learn more about Mobile application
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2 A dev board with a display
A microcontroller, a GPS module, and a small screen showing speed and distance.
- The satisfaction is the object, and this is the object
- Total control over what is shown and stored
- Cold, wet, vibration, and a slow GPS fix under trees
- Write to storage continuously or lose the ride to a power cut
Learn more about Firmware and embedded software
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3 Sync rides home over wifi
The device uploads tracks when it comes back into range of the house.
- Rides land in a proper history without a cable
- Analysis happens on a real screen
- Two schemas and a sync protocol you wrote yourself
- Old firmware in the field syncing against a newer server
Learn more about Mobile app that syncs with a web app
E-ink wall display
A screen on the wall showing today — calendar, weather, bins — that never glows.
What it is
A low-power e-ink panel that refreshes a few times a day with the small set of things a household actually wants at a glance.
How you can build it
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1 A tablet showing a web page
An old tablet on a stand, displaying a page you built.
- No hardware work, and colour if you want it
- The page is just a website you can change freely
- It glows, which is exactly what an e-ink display avoids
- Needs mains power and stays awake
Learn more about Very simple static website
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2 A panel fetching a rendered image
A server composes the whole screen as an image; the device wakes, fetches it, displays it, and sleeps.
- All the layout work happens in comfortable web tools
- The device stays extremely simple, which is why it lasts months
- Rendering for e-ink is closer to poster design than web design
- Refresh rate and battery life are directly opposed
Learn more about App that talks to hardware
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3 Composed entirely on the device
The microcontroller fetches data and draws the screen itself.
- No server to keep running
- Works as long as the wifi and the data source do
- Layout in embedded code is painful compared to a browser
- Every design change means reflashing
Learn more about Firmware and embedded software
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4 The data assembled by a scheduled job
Calendar, weather, and bin collections gathered on a timer into whatever the display reads.
- Sources can be slow or flaky without the display noticing
- Same collected data can feed a phone view
- One more thing that can quietly stop
- Stale data looks identical to fresh data on e-ink
Learn more about Automation that runs without you
Focus or site-cleanup extension
Remove the part of a website that keeps eating your afternoon.
What it is
A browser extension that changes sites you already use — hiding a feed, blocking a site during working hours, stripping clutter, or adding a control the site should have.
How you can build it
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1 The blocking already built into your devices
Screen-time limits and site blocking that ship with the operating system.
- Nothing to build, and it covers apps as well as sites
- Works across every browser at once
- Cannot remove one section of a page you still need
- Easy to override in a moment of weakness
Learn more about The one you might not need to build
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2 An extension hiding one element
Ten lines that remove the feed, the sidebar, or whatever is eating the afternoon.
- Surgical — you keep the site, minus the part that harms you
- Genuinely finishable in an evening
- Breaks whenever the site is redesigned
- Chrome, Firefox, and Safari all differ
Learn more about Browser extension
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3 Scheduled, with per-site rules
Rules that apply only during working hours, configurable per site.
- Removes the all-or-nothing choice
- One extension covers every annoyance you have
- Settings storage and a settings page to build
- Broad permissions are a hard sell if you publish it
Learn more about Browser extension
A command for the thing you do every day
The five-minute chore, reduced to one word in a terminal.
What it is
A small command-line program automating something you personally repeat — resizing images, renaming files, starting a project, fetching a report, formatting data.
How you can build it
-
1 A shell alias or a two-line script
The command you keep typing, saved under a shorter name.
- Five minutes, and it works today
- Nothing to install or maintain
- Falls apart the moment it needs an argument or a decision
- Lives on one machine
Learn more about Command-line tool
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2 A proper script with flags and a dry run
Arguments, a help message, and a preview of what it is about to do.
- Safe enough to point at files that matter
- Understandable when you return to it in a year
- An hour or two rather than five minutes
- Distributing it to a colleague is more annoying than writing it
Learn more about Command-line tool
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3 Run it on a schedule instead of on demand
The same code, invoked by a timer, reporting only when something happened.
- The chore stops requiring you to remember it
- Failures can be made to speak
- Somewhere to run it, and credentials to keep valid
- Silent failure becomes possible for the first time
Learn more about Automation that runs without you
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