JWT Sign
Sign JSON Web Tokens (JWT) with various algorithms including HMAC and RSA for secure authentication.
Overview
This tool lets you craft and sign JSON Web Tokens (JWTs) using HMAC algorithms — HS256, HS384, and HS512 — directly in your browser. Paste your header and payload, supply a shared secret, and get a compact, cryptographically signed token ready for use in authentication flows or API access control. Because all signing is performed client-side via WebAssembly, your secret key and token payload are never transmitted to any server, making this safe to use with real credentials during development and testing.
Common Use Cases
- API Auth During Development — Developers generate signed HS256 tokens on the fly to test protected API endpoints without spinning up an auth service.
- Learning JWT Structure — Security students inspect how the header, payload, and signature combine into a compact dot-separated token by experimenting with different claims and secrets.
- Custom Claims Prototyping — Backend engineers prototype JWT payloads with custom claims (roles, tenant IDs, scopes) before committing the shape to code.
- Debugging Auth Failures — Teams recreate exact token conditions — specific expiry, issuer, or subject values — to reproduce and diagnose token validation errors in staging.
- CI/CD Test Fixtures — QA engineers sign tokens with known secrets to create deterministic test fixtures for integration tests that require authenticated requests.
How It Works
Configure Token Payload
Enter your JWT header and payload data, including claims like user ID, expiration time, and custom fields.
Choose Signing Algorithm
Select the signing algorithm (HS256, RS256, etc.) and provide the appropriate secret key or private key.
Generate Signed JWT
The tool creates a cryptographically signed JWT token that you can use for authentication and authorization.
