What is JWT Decoder & Verifier?
JWT Decoder & Verifier breaks down JSON Web Tokens into their three components: header, payload, and signature. JWTs are the standard for stateless authentication across web and mobile applications. Every JWT carries claims about the user, including identity, roles, permissions, and expiration time, all encoded in a compact, URL-safe string.
Debugging authentication issues often starts with inspecting the JWT. Is the token expired? Does it contain the expected claims? Was it signed with the correct algorithm? DevKit’s JWT tool answers these questions instantly, displaying every field with clear labels and validating the signature when you provide the key.
How to Use JWT Decoder & Verifier
Paste a JWT into the input field. The tool splits it into the three dot-separated segments and decodes the Base64url-encoded header and payload. Each segment is color-coded (header in red, payload in purple, signature in blue) for easy visual identification.
The header section shows the signing algorithm (e.g., HS256, RS256, ES256) and token type. The payload section lists all claims with human-readable labels for standard claims like iss, sub, exp, iat, and aud. Custom claims are displayed with their raw keys and values.
To verify the signature, enter an HMAC secret for symmetric algorithms or paste an RSA/EC public key for asymmetric algorithms. The tool validates the signature and indicates whether the token is authentic and unmodified.
Common Use Cases
- Authentication debugging: Inspect JWTs from OAuth2 or OpenID Connect flows to verify issuer, audience, scopes, and expiration claims.
- API troubleshooting: Decode bearer tokens from API requests to understand why authorization is failing due to missing claims or expired tokens.
- Security auditing: Verify that JWTs use strong signing algorithms and contain appropriate expiration times and audience restrictions.
- Mobile development: Debug token handling in iOS and Android apps by inspecting tokens from keychain or secure storage.
- SSO integration: Decode and compare JWTs from identity providers to verify claim mappings and attribute statements during SSO setup.