About Useful
16 small tools that do their work inside your browser, made by an independent developer.
Why these exist
Most free online tools want your file on their server. You upload a photo to shrink it, or a PDF to split it, and now a copy of that document sits on a machine you know nothing about, governed by a policy you did not read. For a holiday snap that may not matter. For a scan of your ID, a payslip, or a contract, it very much does.
Browsers can do this work themselves now. Canvas can re-encode an image, WebAssembly can parse a PDF, and a background thread can run the whole thing without freezing the page. So these tools take the file, do the work on your own device, and hand it straight back. There is no upload step because there is no server to upload to.
The honest secondary reason: it is also what makes the site affordable to run. Processing files on a server costs bandwidth and CPU; processing them in your browser costs nothing, so the tools can stay free without a subscription or a watermark.
How it is built
The site is static — plain HTML generated ahead of time, no application server. The homepage ships no JavaScript at all; a tool page ships between two and twelve kilobytes, and heavier libraries load only at the moment you actually use the tool. That is why pages open immediately even on a slow connection.
The parts where correctness matters are covered by tests that run on every change: the arithmetic in the calculators, the real output of the PDF operations, and the wiring between each tool's interface and its logic.
What it costs you
Nothing. There are no accounts, no usage limits, no watermarks, and no paid tier. The site carries advertising, placed under rules I set for myself: never inside the tool itself, no pop-ups, no sticky bars, and every ad space reserves its height so the page never jumps while you are using it. If an ad ever gets in the way of finishing a task, that is a bug — please tell me.
What the tools do with your data is set out in the privacy policy. The summary is that your files never leave your device.
Mistakes
Some of these tools tell you about money or legal entitlements. I try hard to get those right — the overtime calculator, for instance, is built from the statute and the ministry's own published interpretations rather than from other people's summaries, and it shows you the source for every figure it uses. It is still a calculator made by one person, not legal advice. If you find something wrong, I would genuinely rather hear about it than not.
Who maintains this
Useful is run by one person. There is no company behind it, no team page, and no investor, which means the usual signals of "who are these people, and why trust them" are not available to you. I would rather say that plainly than dress it up.
So here is what you can rely on instead, and it is stronger than a team page would be: you do not have to take the central claim on trust, because you can check it yourself in about thirty seconds. Open your browser's developer tools, switch to the Network tab, and run any tool on this site with a real file. If a copy of that file were being sent anywhere, you would see the request. There isn't one — not to this site, not to anyone else. That is not a promise about my intentions; it is a fact about the page you are on, and it stays true whether or not you believe anything else written here.
Every other claim on this site is smaller than that one, and most of them follow from it.
Contact
Bug reports, corrections and tool suggestions: [email protected]