JWT Decoder & Inspector

Decode JSON Web Tokens instantly. Runs entirely in your browser. Your tokens never leave your machine.

What is a JWT?

A JSON Web Token (JWT) is a compact, URL-safe token format used for securely transmitting information between parties as a JSON object. JWTs are widely used for authentication and authorization in modern web applications.

Every JWT consists of three parts separated by dots: Header, Payload, and Signature. The header specifies the token type and signing algorithm. The payload contains the claims — statements about the user and additional metadata. The signature is used to verify the token has not been tampered with.

Our JWT decoder splits the token by its dots, base64url-decodes the header and payload, and displays the parsed JSON. This all happens client-side — no data is sent to any server.

JWT Security Tips

  • Never paste production tokens into online tools that send data to a server. This decoder runs entirely in your browser.
  • Always verify the signature server-side before trusting the claims in a JWT.
  • Use short expiration times and refresh tokens to limit the window of exposure if a token is compromised.
  • Store tokens securely — prefer httpOnly cookies over localStorage to mitigate XSS attacks.
  • Never include sensitive information (passwords, secrets) in the payload — JWTs are encoded, not encrypted.
  • Use strong algorithms like RS256 or ES256 instead of HS256 when possible for production systems.

Frequently Asked Questions

Is this JWT decoder safe to use with real tokens?

Yes. This tool runs entirely in your browser using JavaScript. Your token is never sent to any server, stored, or logged. You can verify this by inspecting the network tab in your browser's developer tools.

Can this tool verify JWT signatures?

This tool decodes and inspects JWTs but does not verify signatures. Signature verification requires the secret key or public key, which should only be done server-side in a secure environment.

What are the iat, exp, and nbf fields?

These are standard JWT claims. iat (Issued At) is when the token was created. exp (Expiration) is when the token expires. nbf (Not Before) is the earliest time the token should be accepted. All are Unix timestamps in seconds.

Explore More Free Developer Tools

Check out our full collection of free browser-based developer tools — OG image generators, favicon makers, meta tag checkers, and more.

View All Tools