Browser dev tools.
Nothing leaves this page.
100% client-side · 0 trackers · 0 cookies · verify in DevTools → Network
Decode and verify JWTs (HS256/RS256/ES256) in the browser.
Live match highlighting, capture groups and explanations.
Next 10 runs in your timezone, plus plain English.
Encode and decode with auto-detect and byte counts.
Convert between Unix timestamps and human dates.
Generate TypeScript types and more from a JSON sample.
Run jq filters over JSON, entirely client-side.
Turn CREATE TABLE statements into an entity diagram.
Generate and inspect UUIDs (v4, v7 and friends).
Decode and inspect X.509 / PEM certificates.
Beautify, minify, validate and sort JSON with error locations.
SHA-1/256/384/512 of text, as hex or Base64.
Line-by-line diff of two text or code blocks.
Why dev0?
Most online dev utilities (JWT decoders, regex testers, cert inspectors) are SaaS pages that can log whatever you paste. That's a problem when the thing you're debugging is a production token, a customer payload, or a private key. dev0 runs every tool in your browser: nothing is uploaded, there are no accounts, and you can confirm zero network activity in DevTools → Network. One real URL per tool, so each is easy to bookmark and share.