Formatters, validators, and encoders for JSON, Base64, JWTs, and more — 15 tools that run as JavaScript in your browser tab. Nothing you paste is ever uploaded, logged, or stored.
Developer Tools are formatters, validators, and encoders for the data formats and artifacts developers handle daily — JSON, Base64, JWTs, cron expressions, SQL, CSS, and more. Every tool here runs entirely as client-side JavaScript in your browser: nothing you paste, upload, or drop onto a tool is ever sent to a server, logged, or stored. Open a tool, use it, close the tab — there's nothing left behind. Each one is built around the same IDE-style layout — an editor pane, an action ribbon, and a terminal-style status log — so switching between the JSON Formatter and the SQL Formatter feels like the same tool, not fifteen unrelated ones.
Updated
What it does
Formatters and validators for JSON, CSS, and SQL, with inline error locations instead of a generic "invalid input" message
Encoders and decoders for Base64 and URL-encoded strings, plus a JWT decoder that reads the header/payload without verifying a signature (it has no secret to verify with)
Generators for UUIDs, passwords, and QR codes that run entirely client-side, so a generated password is never transmitted anywhere to be generated
A regex tester, cron expression parser, and diff checker for everyday debugging tasks that don't need a full IDE open
FAQ
Do these tools work offline?
Once a tool's page has loaded, yes — all processing happens locally in your browser's JavaScript engine, so it keeps working even without a network connection.
Is there a size limit on what I can paste or upload?
There's no artificial limit imposed by the tools themselves, only what your browser's memory can handle. Processing runs on the main thread by design, so very large inputs (tens of megabytes) may briefly slow the tab down rather than show a loading spinner.
Why build these instead of using a desktop app?
No install, no account, and no update to manage — open the page and the tool is ready. Because everything runs client-side, you get the privacy of a local tool with the convenience of a link.
Which tool should I use for a JWT vs. a JSON payload?
Use the JWT Decoder for a full token string (three dot-separated Base64url segments) — it splits and decodes the header and payload for you. Use the JSON Formatter for a plain JSON object or array, including the decoded payload the JWT Decoder produces.