JSON Web Tokens (JWTs) are commonly used for API authentication and authorization. Our free JWT Decoder splits a JWT into its three parts — header, payload, and signature — and displays the decoded JSON content.
JWTs consist of three Base64url-encoded parts separated by dots: the header (algorithm and type), the payload (claims like user ID, expiration, permissions), and the signature (verifies the token has not been tampered with).
The decoder also checks token timing — showing whether the token has expired based on the 'exp' claim and when it was issued based on the 'iat' claim. Everything runs in your browser for complete privacy.