A JWT decoder is an essential tool for developers working with JSON Web Tokens. Paste any JWT and instantly see the decoded header, payload, and signature in a readable format — no installation needed.

JSON Web Tokens are widely used for authentication and authorization in REST APIs, OAuth 2.0 flows, and single-sign-on (SSO) systems. Debugging a JWT manually requires base64url decoding — this tool does it in one click.

What you can do with this JWT tool

Decode JWT header to inspect algorithm (HS256, RS256, ES256) and token type
Read payload claims: sub, iss, exp, iat, aud, custom claims
Check token expiry — see exactly when a JWT expires in human-readable format
Verify JWT signature using a secret or public key
Detect common JWT security issues (none algorithm, missing expiry, weak secrets)

JWT structure explained

A JWT consists of three base64url-encoded parts separated by dots: header.payload.signature. The header specifies the signing algorithm. The payload carries the claims. The signature ensures the token hasn't been tampered with.

FAQ

Is it safe to paste a JWT into an online decoder?

For production tokens, use this tool in a private/incognito window. The decoder runs entirely in your browser — nothing is sent to a server. However, avoid pasting tokens that grant sensitive long-lived access.

Can this tool verify JWT signatures?

Yes — paste your HMAC secret or RSA/EC public key to verify the signature and confirm the token hasn't been modified.

What is the difference between JWT and OAuth?

OAuth 2.0 is an authorization framework. JWT is a token format often used to carry OAuth access tokens or OpenID Connect ID tokens.