JWT Claims Builder

What is JWT Claims Builder?

JWT Claims Builder creates custom JSON Web Token payload structures with standard registered claims (iss, sub, aud, exp, nbf, iat, jti) and custom claims, generating the complete JWT payload ready for signing. It validates claim types, computes Unix timestamps for expiration and not-before fields from human-readable durations, and warns about security-sensitive claims like admin: true or role: superuser. The tool also generates the complete unsigned JWT (header.payload) for testing and development.

Authentication architects designing token structures, backend developers implementing JWT-based auth, and security engineers reviewing token claim designs for vulnerabilities. The tool runs entirely in your browser — your data never leaves your device.

How to Use JWT Claims Builder

1. Set the registered claims — issuer (iss), subject (sub), audience (aud), and expiration duration
2. Add custom claims for your application — roles, permissions, tenant ID, or any domain-specific data
3. Review the computed timestamps and the complete payload JSON
4. Copy the payload for use in your token generation code or test the unsigned JWT in your decoder

Common Use Cases

• Designing JWT token structures for new authentication systems with proper claim choices
• Creating test JWT payloads for development and QA environments
• Documenting the expected claims and their formats for API authentication specifications
• Prototyping role-based access control schemes using custom JWT claims

Pro Tips

• Keep JWT payloads small — every claim adds to the token size which is sent with every HTTP request; for complex permissions, store a permission ID in the JWT and look up details server-side instead of embedding the full permission set
• Always include jti (JWT ID) as a unique identifier — it enables token revocation by blacklisting specific token IDs, which is otherwise impossible with stateless JWTs
• Set exp (expiration) as short as practical — 15 minutes for access tokens, 7-30 days for refresh tokens; short-lived access tokens limit the damage window if a token is leaked

Why Use This Tool?

• Privacy-first: All processing happens locally in your browser. No data is transmitted to any server.
• No installation required: Works in any modern browser on desktop or mobile.
• Completely free: No account, no credit card, no usage caps.
• Fast and reliable: Powered by modern Web APIs for near-instant results.

Related Concepts

Learn more about related topics: JWT claims, RBAC, Token expiration, RFC 7519.

Frequently Asked Questions