What it is
devtul.fun collects twelve utilities that come up constantly while working: formatting JSON, comparing text, testing regular expressions, computing hashes, decoding JWTs, generating cron schedules. They share one property: they run entirely in the browser.
There is no account, no upload, and no request that reaches a server of mine — this site does not even have an application server, only a pile of static files on a CDN. What you paste exists in the memory of the current page and disappears when you close the tab.
Why rebuild them
None of these tools is technically difficult; most of them are a few dozen lines of code. What goes wrong in practice is the opposite problem: many sites doing the same thing wrap a simple operation in request round-trips, permission checks and loading spinners, then fill the rest of the page with everything else.
What I wanted was unglamorous: open it, paste, get the answer, close it. No sign-up, no pop-ups, no limits.
How it is built
- A fully static site with no backend, hosted on Cloudflare
- Plain JavaScript, no framework — pages keep working offline once loaded
- Only three open-source libraries, all MIT or BSD: Markdown parsing, YAML parsing and a diff algorithm
- Everything else is written here: the JSON tree, the diff renderer, the cron parser and its plain-language description, and the cryptographic hashes
Feedback
Bug reports and tool requests are welcome. One caveat: features that need a server will not be added — online storage, user accounts or tools that call third-party APIs would break the promise that your data never leaves the device.