JWT Decoder

Decode & inspect JSON Web Tokens (JWT). View the Header, Payload (Claims), and Signature of any token. Useful for OAuth debugging, API testing, and security analysis.

What Is a JWT (JSON Web Token)?

A JWT is a compact, cryptographically signed token used for securely transmitting information between parties. Popular in authentication systems such as OAuth 2.0, OpenID Connect, and modern web APIs.

JWT Structure Explained

header.payload.signature

Header: Defines the signing algorithm (HS256, RS256, ES256) and token type.
Payload: Contains claims such as user ID, expiration time, issuer, and roles.
Signature: Ensures the token has not been altered.

How Does JWT Authentication Work?

After a user logs in, the server generates a JWT and signs it using a secret or private key. The client stores this token and sends it with every request. Servers verify the signature to authenticate the user without storing sessions.

Is This JWT Decoder Safe?

Yes — decoding happens 100% in your browser. Tokens are never uploadedor sent to a server. This tool is safe for debugging development tokens.

Note: This tool decodes JWTs but does NOT validate or verify signatures.