JWT Decoder
Decode and inspect JSON Web Tokens instantly.
What Is a JWT Token?
A JSON Web Token (JWT) is a compact, URL-safe string used for securely transmitting information between parties. It consists of three Base64-encoded parts separated by dots: a header (algorithm and type), a payload (claims and data), and a signature. JWTs are widely used for authentication, authorization, and information exchange in web applications.
How Do I Decode a JWT Token?
Paste your JWT string into the input area and the tool instantly decodes and displays the header and payload as formatted JSON. It also shows the signature and identifies the signing algorithm. The tool validates the structure and highlights any formatting issues.
Can This Tool Verify JWT Signatures?
This tool decodes and displays JWT contents but does not verify cryptographic signatures, as that requires the secret key or public key. It is designed for inspection and debugging — to see what claims a token contains, check expiration times, and understand the token structure.
Is It Safe to Paste JWTs Into an Online Tool?
With ToolsFast, yes. The decoder runs entirely in your browser — your token is never sent to any server. However, be cautious with production tokens, as they may contain sensitive user data. Expired or test tokens are always safe to inspect. Never share valid tokens publicly.
What Are Common JWT Claims?
Standard claims include: iss (issuer), sub (subject/user ID), aud (audience), exp (expiration timestamp), nbf (not before), iat (issued at), and jti (unique JWT ID). Custom claims can contain any application-specific data like user roles, permissions, or email addresses. The exp claim is especially important — always check it to verify a token has not expired.
How Long Should JWT Tokens Last?
Access tokens should have short lifetimes — typically 5 to 15 minutes — to limit the damage if a token is compromised. Refresh tokens can last longer (hours to days) since they are stored more securely and can be revoked. The exp claim in the payload specifies when the token expires as a Unix timestamp. This tool shows the expiration in human-readable format so you can quickly verify token validity.