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JWT Decoder

Decode and inspect JSON Web Tokens (JWT). View header, payload, and verify expiration.

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What is a JWT Decoder?

A JWT (JSON Web Token) decoder parses the three parts of a JWT — header, payload, and signature — and displays them as readable JSON. JWTs are the standard for stateless authentication in modern web applications, used by OAuth 2.0, OpenID Connect, and countless API platforms. Each token is a Base64URL-encoded string containing claims (user info, permissions, expiration) that your application can read without making a database call. This tool decodes tokens instantly in your browser for inspection and debugging.

How to Use This Tool

  1. Paste your JWT token into the input field. The token should have three dot-separated segments (header.payload.signature).
  2. View the decoded sections immediately — the header shows the signing algorithm, the payload shows all claims and user data.
  3. Check expiration status — the tool automatically detects the exp claim and tells you whether the token is still valid or expired.

Common Use Cases for Developers

  • Authentication debugging: Inspect tokens returned by your auth service to verify claims, roles, and scopes are correct.
  • Token expiration issues: Quickly check if 401 errors are caused by expired tokens without writing parsing code.
  • OAuth flow testing: Decode access tokens and ID tokens during OAuth 2.0 / OIDC implementation to verify the identity provider is returning expected claims.
  • API troubleshooting: When an API rejects a token, decode it to check if required claims (audience, issuer, scopes) are present.
  • Security audits: Verify that sensitive data isn't inadvertently exposed in JWT payloads (remember: JWTs are encoded, not encrypted).

Tips & FAQ

  • JWTs are not secure storage: The payload is only Base64-encoded — anyone can decode it. Never put secrets, passwords, or sensitive PII in JWT claims. Use encryption (JWE) if payload confidentiality is required.
  • This tool cannot verify signatures: Signature verification requires the secret key or public certificate. This decoder only reads the token structure — it cannot confirm the token hasn't been tampered with.
  • Common JWT claims: sub (subject/user ID), iss (issuer), aud (audience), exp (expiration), iat (issued at), nbf (not before), jti (unique token ID).