Free tool

JWT quantum risk checker

Paste a JWT to decode its header and check the signing algorithm for quantum risk. Only the header is read — no secret or private key required, and nothing leaves your browser.

Paste a JWT (only the header is decoded)

Runs entirely in your browser. No secret/private key needed.

Disclaimer: Symmetric HMAC algorithms (HS256/384/512) are a different risk category from public-key signatures. They are not broken by Shor’s algorithm; their practical concern is key distribution. Public-key signatures (RS*, PS*, ES*, EdDSA) are the quantum-vulnerable ones.

Read more about post-quantum risk in JWT signing.