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A JSON Web Token is a signed, base64url-encoded token of a header, payload, and signature used to carry identity and claims. It is a target because flawed verification, such as trusting the header's algorithm or a weak signing key, can let an attacker forge tokens and impersonate any user.
Set the header's alg field to none and strip the signature; servers that honor it accept the token as valid without any cryptographic check. The JWT Payloads generator can mint these unsigned tokens, along with tampered claims, so you can test whether a backend rejects the none algorithm.
If a server uses the RSA public key to verify but a library lets you switch alg to HS256, you can sign a forged token using that public key as the HMAC secret. The generator supports signing with arbitrary algorithms and keys so you can test this confusion as well as weak-secret HMAC cracking.
Yes. The JWT Payloads generator creates and signs tokens entirely client-side, so your keys, secrets, and tokens never leave your device. It is free and intended only for authorized testing of systems you own or are permitted to assess.