About useformatter.dev
useformatter.dev is a small collection of everyday developer utilities — formatting JSON, decoding a token, hashing a string, converting a timestamp — built around one rule: your data never leaves your browser.
Why it exists
Most online developer tools work by sending whatever you paste to a server. For a scratch snippet that's fine. For a production JWT, an API response containing customer records, or a config file with internal hostnames, it's a quiet data leak — and it's usually the fastest option available when you're mid-debug, so people do it anyway.
This site is the alternative: the same conveniences, with the processing moved into your browser where the data already is. You can verify the claim rather than take it on faith — open your browser's network panel while you use any tool, or load a page and turn off your connection. Everything keeps working.
How it's built
Deliberately plainly. There is no framework, no component library, and no analytics bundle. Each page is hand-written HTML with a small amount of vanilla JavaScript, and the whole site is static files served from a CDN.
The engines behind the tools are written from scratch rather than pulled from dependencies — the JSON and YAML parsers, the syntax highlighter and code editor, the line-diff algorithm, the QR encoder, the hash functions. That's partly a privacy decision (fewer third-party scripts means fewer places your data could go) and partly a performance one: pages load in milliseconds and work offline once visited.
The parts that are easy to get subtly wrong — the diff algorithm, YAML parsing, UUID generation, hashing — are covered by an automated test suite that checks them against independent references, because a formatter that silently corrupts your data is worse than no formatter.
What it costs
Nothing. There are no accounts, no sign-ups, no usage limits, and no paid tier. The site carries advertising to cover the domain and running costs.
Worth being precise about that, since it's the one third-party element on the site: ads are served by Google, which may use cookies to select them. That is entirely separate from the tools — the ad system never receives the content you paste, because that content never leaves your device in the first place. The privacy page spells out exactly what is and isn't collected.
What's here
Fifteen tools at the moment, grouped into JSON and data (formatter, unescape, JSON ↔ CSV, JSON ↔ YAML, diff), encoding (Base64, URL), cryptography (JWT, hash, HMAC), and generators (UUID, timestamp, current time, QR code). There are also written guides explaining the formats behind the tools in more depth.
New tools get added when they're genuinely useful and can be done properly in-browser. Anything that would require sending your data to a server doesn't get built.
Who's behind it
It's an independent project, built and maintained by one developer rather than a company. That means it moves quickly, and it means feedback goes straight to the person who can act on it — if something is broken, wrong, or missing, get in touch.