JWT Builder & Signer
Builds a JSON Web Token from your header and payload claims and signs it with an HMAC secret (HS256, HS384 or HS512), producing a token you can paste straight into an Authorization header. Also verifies a token against a secret and flags expiry.
Runs 100% in your browser — keys and data never leave your device.
Read the full guide to this tool
Notes
- The header and payload are only Base64url-encoded, not encrypted — never put secrets in a JWT. The signature only proves integrity and authenticity.
- Always set an exp (expiry) claim, and reject the "alg": "none" token — accepting it is a classic authentication bypass.
- Runs 100% in your browser — keys and data never leave your device.
Explore the idea
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