Security & Privacy

The problem with most online dev tools

Paste a JWT into a random online decoder, and where does that text actually go? For a huge number of tool sites, the answer is: to their server first, then back to your browser to display. The tool works the same either way from your point of view — but one version means a stranger's server logs (or a breach of that server) now has a copy of a token that might carry a user's session, roles, or internal API scopes.

The same risk applies to every tool on a site like this one: a hash generator that hashes server-side has seen your plaintext first. A "JSON formatter" that posts your payload to an API before formatting it has seen your production data, possibly including customer records, in transit and in whatever logs that server keeps.

What "runs entirely in your browser" actually means, technically

Every tool on FreeDevToolsKit is built using only client-side JavaScript — functions like JSON.parse(), atob()/btoa(), crypto.subtle.digest(), and crypto.getRandomValues(), all of which execute locally in the JavaScript engine your browser already has. None of these functions make a network request. There is no backend endpoint that receives your input, because none of these tools have one to send it to.

This is different from a site merely promising not to log your data server-side — a promise you have no way to verify. Here, there's structurally nothing to log, because the data structurally never arrives at a server in the first place.

Verify it yourself — don't take our word for it

You don't need to trust this claim on faith. Open any tool page, then open your browser's Developer Tools (F12, or right-click → Inspect), switch to the Network tab, and use the tool — paste a JWT, hash some text, generate a UUID. Watch the Network panel while you do it. Aside from the initial page load (the HTML/CSS itself), you'll see zero new requests fire when you interact with the tool. That's not a claim; it's something you can watch happen in real time.

Why this matters specifically for JWTs, API keys, and production data

Developers routinely need to inspect real, sensitive artifacts during debugging: a JWT carrying a live user's session, an API key while troubleshooting a misconfigured request, a slice of actual production JSON while chasing down a data bug. Pasting any of these into a tool that transmits them server-side means that data now exists somewhere outside your control — a third party's access logs, error tracking, or database, indefinitely, regardless of what their privacy policy promises about intent.

A tool that never transmits the data at all removes that risk category entirely, rather than asking you to trust a promise. That's the actual, structural reason "runs in your browser" is worth caring about — not because it sounds reassuring, but because it changes what's technically possible to go wrong.

Two exceptions on this site, disclosed plainly

Every tool that could be built to run purely client-side is. If any tool on FreeDevToolsKit ever needs to reach an external service for a legitimate reason (for example, checking a value against a public API), that behavior will be called out explicitly on that tool's own page, exactly like this. If a tool's page doesn't mention it, none is happening.