About JWT Dev Tools
A fast, private JWT decoder built by engineers, for engineers.
JWT Dev Tools is a free online JWT decoder and inspector. We built it because debugging JSON Web Tokens shouldn't mean pasting sensitive credentials into a site that ships them off to a server. Every decode, claim explanation, expiry check, and signature verification happens entirely in your browser.
What we do
The tool decodes any JWT into its header, payload, and signature, explains every standard claim in plain
English, flags security risks like alg: none and missing aud, and verifies
HS256, RS256 and ES256 signatures using the browser's native Web Crypto API.
Our principles
- Privacy first. Your token never leaves your device. There is no backend that sees it.
- No friction. No signup, no login, no paywall. Open the page and paste.
- Accuracy. Claim explanations and security warnings reflect current JWT and OAuth best practices.
- Speed. The page is static and loads in milliseconds, even on slow connections.
Who it's for
Backend and frontend developers, QA engineers, security reviewers, and anyone integrating with identity providers such as Auth0, Firebase, AWS Cognito, Azure AD, and Google. If you work with bearer tokens, this is built for you.
Why trust it
The decoding logic is client-side JavaScript that you can inspect in your browser's developer tools. Because nothing is transmitted, there is no log, no database, and no analytics on the contents of your tokens. We only measure anonymous, aggregate page usage to understand traffic — never token data.