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CORS Origin Null Literal Distinction Tool

Compute cors origin null literal distinction from explicit bounded inputs.

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Description

Treat the exact literal null as opaque true.

Web protocol data has several layers: a complete message or URL, individual fields or components, and the literal tokens within them. Delimiter presence, spelling, comparison rules, and parser normalization can affect results. A check of one component needs its stated scope before it can be used in a larger parser or policy decision.

Treat the exact literal null as opaque true.

When to use this tool

Use CORS Origin Null Literal Distinction when you need one stated URL, header, or protocol-component check in a diagnostic or parser workflow. Supply the input level specified below.

How to use the tool and how it works

  1. Enter origin. Use the units and conventions below.
  2. Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
  3. Read opaque, serializedOrigin. Inspect opaque before interpreting the associated values.

Treat the exact literal null as opaque true. Otherwise parse origin, require HTTP or HTTPS, and require its serialized origin to equal the entire supplied string; return opaque false and that origin.1

Input fieldMeaning and unitsAccepted input
originOriginRequired. Text; maximum UTF-16 length 8192.
Output fieldInterpretationReturned shape
opaqueOpaqueRequired. Boolean.
serializedOriginSerialized OriginRequired. Text; maximum UTF-16 length 8192.
json
{
  "input": {
    "origin": "null"
  },
  "output": {
    "opaque": true,
    "serializedOrigin": "null"
  }
}

Limitations and assumptions

  • Canonical spelling is required, so paths, trailing slash, explicit default ports, or case-normalizable spellings can be rejected. This does not authenticate an Origin header or determine CORS authorization.
  • The field tables state structural bounds; the mechanics also specify cross-field constraints. Malformed inputs and unsupported domains cause errors. A successful false flag, empty branch value, or zero placeholder has the meaning stated above and is distinct from an input error.

Alternative or Complementary methods

Use a complete URL or header parser when the task involves an entire field or message. Test actual browser, server, or cache behavior separately when a security or protocol decision depends on more than this component.

References

  1. Calculation and input contract: web/cors-origin-null-literal-distinction — tool.io

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