JWT tools — free JSON Web Token decoder & inspector

JSON Web Tokens (JWTs) are compact, URL-safe strings that usually carry signed claims between an authorization server and your APIs. Our free tools help you inspect what is inside a token for debugging—never as a substitute for server-side verification. Open the JWT decoder, then read JWT explained for busy developers for the full picture on claims, lifetimes, and why decode ≠ trust.

JWT decoder

Paste a token, view JSON for header and payload, and see expiry at a glance.

What are JSON Web Tokens?

A JWT is a string with three parts (header, payload, signature) separated by dots. The header and payload are Base64url-encoded JSON: you can read them in any JWT decoder. The signature proves the token was issued by a party that holds the right key; verifying that signature on your API is what makes the token trustworthy. Without verification, anyone can forge a payload—so treat our browser tool as a microsope, not a gate.

JWT structure: header, payload, signature

The most common form looks like header.payload.signature. The header names the signing algorithm (for example RS256 or HS256). The payload carries claims: OpenID-style fields like sub, time windows like exp and iat, and app-specific data. The signature covers the bytes header.payload using the issuer's key. Our online JWT decoder pretty-prints the first two segments only; it does not call your identity provider or check the signature.

Common JWT use cases

  • OAuth 2.0 / OpenID Connect: access tokens and ID tokens as JWTs for APIs and SPAs.
  • API gateways: verifying a bearer token before routing to microservices.
  • Single sign-on: passing identity and session claims between domains (with careful cookie and CORS design).
  • Service-to-service auth: mTLS or signed JWTs between backends—still verify on the receiving service.

JWT security best practices

  • Prefer short-lived access tokens and explicit refresh strategies your threat model allows.
  • Always verify issuer, audience, exp, and signature on the server using maintained libraries.
  • Ship JWTs over HTTPS; never treat a decoded token in a blog or tool UI as an authorization decision.
  • Rotate signing keys and monitor for alg: none or algorithm confusion issues in your stack.

For encoding work next to token debugging, use Base64 encode and the rest of the developer tools directory.