JWT Decoder
Decode JSON Web Tokens to inspect header, payload, and signature. No verification — purely for inspection.
What is a JWT?
A JSON Web Token (JWT) is a compact, URL-safe token format used for securely transmitting information between parties. JWTs consist of three parts separated by dots: Header, Payload, and Signature. The header and payload are Base64-encoded JSON objects, while the signature verifies authenticity.
This tool decodes the Base64-encoded parts to show you the header and payload contents. It does NOT verify the signature — it's purely for inspection and debugging.
JWT Structure
Header: Contains token type (JWT) and signing algorithm (e.g., HS256, RS256). Payload: Contains claims (data) such as user ID, expiration time, and custom fields. Signature: Cryptographic signature to verify token hasn't been tampered with.
Security Note
Never trust JWT data without verifying the signature on your server. This tool is for inspection only — it cannot and does not verify signatures. Always validate JWTs server-side before trusting their contents.