JWT Decoder & Inspector

What is a JWT Decoder & Inspector?

A JWT decoder parses and displays the contents of JSON Web Tokens (JWTs) in a human-readable format, allowing developers to inspect authentication tokens, debug API authorization issues, and verify token claims without needing a private key or secret. JWTs are the standard authentication token format used by OAuth 2.0, OpenID Connect, and countless REST APIs. A JWT consists of three Base64url-encoded sections separated by dots: the header (containing the algorithm and token type), the payload (containing the claims — data assertions about the user or session), and the signature (used to verify the token was not tampered with). The header and payload sections can be decoded and read by anyone with the token — they are not encrypted, only encoded. The JWT Decoder decodes all three sections, displays the header and payload as formatted JSON, calculates the time remaining until the token expires (from the exp claim), and shows the issued-at time (iat claim) in human-readable form. Note that signature verification requires the server's secret key and is not performed client-side.

How to Use JWT Decoder & Inspector

1. Paste your JWT token — the full three-part token including both dot separators — into the input field.
2. Click 'Sample' to load an example JWT and see all three decoded sections.
3. Click ⚡ Decode or press Ctrl+Enter to parse the token and display its contents.
4. Review the decoded header (algorithm, token type) and payload (all claims) in formatted JSON.
5. Check the expiry information — the tool shows whether the token is still valid and how much time remains.
6. Use the decoded claims to debug authentication issues in your application or API integration.

Frequently Asked Questions