JWT Decoder & Verifier

The JWT Decoder instantly parses JSON Web Tokens (JWTs) into their three constituent parts — header, payload, and signature — displaying each in a readable, formatted view. It's an essential debugging tool for backend developers, API integrators, and security engineers who need to inspect token contents, verify claims, check expiration times, and understand token structure without installing CLI tools or writing code.

Paste any valid JWT and the decoder immediately shows the algorithm and key ID from the header, all standard and custom claims in the payload (including exp, iat, iss, sub, aud, and any custom data), and the raw signature. The tool automatically calculates human-readable timestamps for exp and nbf claims, so you can instantly see if a token is expired or not yet valid — critical for debugging authentication flows.

This is a decode-only tool: it reads and displays token contents but never attempts to verify the signature against a secret or public key. This means it's safe for inspecting third-party tokens, and your tokens are never sent anywhere. All decoding is pure client-side base64url parsing.