Referrer Extractor
ExtractactualRefererfieldfrom supplied raw request header lines only; singleabsoluteHTTP(S) branch, no fetch, Referrer-Policy decision or trust/authenticity inferred from spoof able header.
Description
The HTTP Referer request field records a referring URL when a client sends one.
The HTTP Referer request field records a referring URL when a client sends one.1
Its presence depends on request context and policy, and the supplied field alone does not authenticate the referring site. The calculation and input requirements are explained below.
When to use Referrer Extractor
Paste the supplied raw request-header lines.
How to use Referrer Extractor and how it works
- Prepare the measurements or independently established model inputs described below, with matching units and observation scope.
- Enter the required fields and run Referrer Extractor.
- Read the result fields using the formula, output units, signs and ordering explained below.
- Correct any rejected inputs and rerun; interpret the result within the stated model and its assumptions.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| actualRawRequestHeaderLines | Actual Raw Request Header Lines. Use the units and matching context stated in the calculation below. | string | Required; other constraints below |
Paste the supplied raw request-header lines. Split on LF with optional CR and select lines beginning exactly with Referer: case-insensitively; leading whitespace is not accepted as a field prefix. Multiple matching fields are an error. With none, return present=false and an empty URL. Otherwise trim the field value, parse it as an absolute URL, require HTTP or HTTPS and return the normalized href with present=true. The header's spelling is Referer. No request, policy decision or authenticity check occurs.
matchingLines=caseInsensitiveLinePrefix('Referer:'); result=normalizedAbsoluteHttpUrlOrAbsent Apply the input ordering, units and branch conditions stated above.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the calculated or selected fields below. | object |
| result.observedRefererPresent | Observed Referer Present. Interpret its unit, sign, order or availability flag as explained above. | boolean |
| result.observedRefererUrl | Observed Referer Url. Interpret its unit, sign, order or availability flag as explained above. | string |
{
"input": {
"actualRawRequestHeaderLines": "Host: example.com\nReferer: https://source.example/path"
},
"output": {
"result": {
"observedRefererPresent": true,
"observedRefererUrl": "https://source.example/path"
}
}
}Limitations and assumptions
The calculation uses the supplied observations and model inputs. It does not collect measurements, select a reference population or coefficient, or establish that the model applies to the actual case. The stated branch conditions and output units remain part of the result.
All fields require explicit values. Unexpected fields, wrong types, nonfinite numbers and sparse arrays are rejected. Alignment, bounds and supported-token rules are explained above; extremely large inputs or nonfinite results can also fail. Input errors differ from successful false comparisons, unavailable-domain flags and empty match lists.
Alternative or Complementary methods
Use Referrer Attribute Parser for a complementary operation: A referrerpolicy attribute names a policy for controlling referrer information.
Use Content Encoding Detector for a complementary operation: Content-Encoding declares transformations applied to an HTTP representation, such as compression.
References
-
Referrer Extractor — tool.io
Similar or alternative tools
- Referrer Attribute Parser
A referrerpolicy attribute names a policy for controlling referrer information.
- Content Encoding Detector
Content-Encoding declares transformations applied to an HTTP representation, such as compression.