I have been writing production software for more than ten years. I started on backend systems in Python and Java, moved into full-stack work with Node.js, and for the last several years I have focused almost entirely on TypeScript, React, and Next.js. Before DevToolHQ I built applications used by paying customers, shipped mobile apps on the App Store and Play Store, and worked through the full cycle of hiring, on-call rotations, incident reviews, and the slow grind of getting performance numbers down to where they need to be.
DevToolHQ exists because I needed these tools myself and I did not trust the versions already online. When you decode a JWT that contains a real customer identifier, or hash a string that might be part of a signing key, sending that data to someone else's server is a small but real risk. Pasting sensitive JSON into a random site to pretty print it has the same problem. I wanted a set of utilities where I could point a colleague at a URL and tell them, truthfully, that nothing they type is ever sent anywhere.
Every tool on DevToolHQ runs entirely in the browser. The JWT decoder uses jsrsasign to parse and verify tokens locally. The hash generators use CryptoJS and the native Web Crypto APIwhen the algorithm is supported. The URL parser uses the browser's native URL constructor. Nothing is uploaded, nothing is proxied, and there is no server-side computation involved in any of the results you see. The network tab is the proof.
I write every tool with the assumption that a skeptical engineer will open devtools and check. That shapes the whole stack: React for the UI, no tracking on tool pages, small focused libraries that are easy to audit, and a strict rule against any analytics call that includes user input. I keep the dependency list short on purpose so the bundle stays small and the behavior stays predictable.
The site is updated constantly. Bug fixes and small improvements ship every week, and I add new tools roughly once a month based on what I actually reach for during my day job. The methodology page describes exactly how the client-side architecture works, which libraries power which tool, and why I made the trade-offs I did.
If you spot a bug, want a tool added, or want to check that a specific tool really does what I say it does, write to hello@devtoolhq.com. I read every email myself.