I've been building a small line of freelance business tools — a rate calculator, proposal generator, contract generator, and invoice/cash flow tracker — and every one of them is a single .html file. No npm install, no build step, no server, no database, no account system. You download the file, double-click it, and it opens as a fully working app in your browser.
Why go this route
Every SaaS alternative to these tools follows the same pattern: sign up, hand over your email, your data lives on their server, pay monthly forever. For something a freelancer might use a handful of times a week, that's a lot of overhead — both for the user (yet another account, yet another subscription) and for me (auth, a database, hosting, uptime, all for a tool that doesn't need any of it).
So I asked: what's the simplest thing that could possibly work?
- All state lives in
localStorage. No backend needed. - All logic is client-side JS. No build tooling — just a
<script>tag. - Printing/PDF export uses
window.print()with print-specific CSS instead of a PDF library. - Styling is plain CSS with custom properties for theming — no framework.
The whole thing is close to how the web worked in 2010, and it turns out that's still enough for a real, useful tool.
What this buys you
- Zero infrastructure to maintain. No server to keep up, no database to back up, no auth to secure.
- Privacy by default. Nothing the user types ever leaves their machine, because there's nowhere for it to go.
- It works forever. No dependency will go unmaintained and break it. No API will get deprecated. Open the same file in ten years, it still works.
- Distribution is trivial. It's just a file. Email it, put it on a USB stick, whatever.
The tradeoffs
To be upfront about the downsides:
- No sync across devices (by design — that would require a backend).
- No collaboration features (same reason).
- Users are responsible for their own backups (their browser's storage, not "the cloud").
For a lot of tools people reach for a subscription SaaS for, none of that matters.
Try it
I bundled the four tools together if anyone wants to see the approach in practice: Complete Freelance Business Kit. Happy to go deeper into any of the implementation details in the comments — genuinely curious whether other people think "boring single-file tools" is underused as a product format.
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