JWT Decoder
Decode and inspect JSON Web Tokens (JWT). View header, payload, and expiration status.
What is a JWT?
JSON Web Token (JWT) is a compact, URL-safe token format used for securely transmitting claims between parties. A JWT consists of three Base64URL-encoded parts separated by dots: a header specifying the algorithm, a payload containing claims, and a cryptographic signature.
Paste a JWT token into the input field and the tool instantly decodes the header and payload, displaying all claims in a readable format. It also checks the expiration (exp) claim and shows whether the token is still valid. A sample token is provided for quick exploration.
JWTs are the backbone of modern web authentication — they are used in OAuth 2.0 flows, single sign-on (SSO) systems, API authorization, and stateless session management. Developers frequently need to inspect tokens during debugging, security auditing, and integration testing.
The header typically contains the signing algorithm (HS256, RS256) and token type. The payload holds registered claims like sub (subject), exp (expiration), iat (issued at), and iss (issuer), along with any custom application claims. Note that JWT payloads are encoded, not encrypted — anyone can read the contents without the signing key.