Verify a JWT HMAC signature (HS256/HS384/HS512) with your secret online, computed in your browser.
Check whether a JWT's HMAC signature is valid for a given secret, and whether the token has expired. Verification runs locally with Web Crypto, so your secret stays in the browser.
The HMAC family — HS256, HS384 and HS512. RS/ES (asymmetric) tokens are not verified here.
The signature matched but the token is expired (exp in the past). valid combines both signature and expiry.