Signed JWT Test Fixture Builder

How to use Signed JWT Test Fixture Builder

Create a local HS256 compact JWT test artifact from supplied JSON claims and an explicitly provided test key. Keep the exact JSON payload bytes, a fixed HS256 protected header and an optional key identifier. Copy a deterministic fixture for a test suite without sending an authentication request.

1. Provide json claims object, local test key: never included in the report, optional protected-header key identifier.
2. Choose the supported mode and run the tool. Review its assumptions and any reported errors.
3. Copy the result or download a separate output; reset to clear the current form.

Good to know

• Claims are a JSON object of at most 16,384 UTF-8 bytes, 100 top-level members and 40 levels. Duplicate and prototype-related keys, nonfinite/underflowed numbers and numeric magnitudes above 1 trillion are refused. The original payload spelling is preserved instead of canonicalizing it.
• Only fixed HS256 with typ JWT, optional kid up to 200 UTF-8 bytes and 32–1,024 decoded key bytes. The key input is at most 4,096 UTF-8 bytes. UTF-8, complete hexadecimal bytes and canonical unpadded Base64url are supported. Byte length alone does not establish random-key strength.
• Selected registered claim types are checked; required claims, StringOrURI application meaning, issuer/audience trust, timestamps, replay policy and authorization are not validated. No time or claim is automatically inserted.
• Use test keys you are authorized to handle. Generated tokens are readable signed artifacts, not encryption or a login grant. WebCrypto/HTTPS is required; no endpoint, key URL, credential store or network request is used.
• The separate JSON report is limited to 500,000 characters, including formatting; reduce the source if the report exceeds that bound.
• Inputs are processed on this device and are not automatically saved or uploaded.