Paste a JWT and see what is inside: the header, payload, and whether the signature looks valid.

JWT decoder for inspecting header and payload claims. Decodes Base64url-encoded segments and displays algorithm, kid, exp, iat, iss, sub, and any custom claims. Signature verification requires the key.

Splits the JWT on '.' delimiters; Base64url-decodes (RFC 4648 section 5) header and payload segments without padding normalisation. Displays decoded JSON with claim interpretation: exp/iat/nbf rendered as human timestamps, standard IANA claim names annotated. Signature segment shown as hex; verification against a provided HMAC secret or RSA/EC public key performed via SubtleCrypto.verify.