replace-xhr-response

The replace-xhr-response snippet replaces the response of a XHR request if the response text matches a given regular expression pattern.

Parameters

Name	Description	Mandatory	Default
search	String or regex pattern run against the stringified XHR response. If the value starts with `jsonpath(`, it is treated as a JSONPath query instead.	Yes	n.a.
replacement	Everything that matches the regex will be replaced with this. In JSONPath mode it is interpreted as a typed value instead of literal text.	No	empty string
needle	Replacement only happens if needle text is present in the response. Enclose in `/` for regex.	No	empty string

JSONPath mode

When search starts with jsonpath(, the response is parsed as JSON, the query is evaluated against it, every matching property is replaced, and the result is re-serialised. Use this when the value to change is a structured field rather than a text pattern — it avoids regex-matching a serialised payload, and lets you inject a real boolean or empty array instead of a string.

If the response is not valid JSON, or the query fails to evaluate, the rule is skipped and the response is left unchanged.

For the supported query syntax, see JSONPath evaluator.
For the values replacement accepts in this mode, see the value table on override-property-read.

Filter examples

Filter	Result
`replace-xhr-response '/ads:\\\\[(.*?)\\\\]/'`	Removes anything like `ads:[any-string]` from every response body.
`replace-xhr-response 'serve-ads:true' 'serve-ads:false'`	Replaces the string in the response body.
`replace-xhr-response 'serve-ads:true' 'serve-ads:false' example.com`	Replaces only if the response contains "example.com".
`replace-xhr-response 'jsonpath($.ads[*].enabled)' false`	JSONPath mode. Sets `enabled` to the boolean `false` on every element of the `ads` array.
`replace-xhr-response 'jsonpath($..trackingId)' null`	Sets every `trackingId` property at any depth to `null`.
`replace-xhr-response 'jsonpath($.slots)' emptyArray`	Replaces the `slots` array with a real empty array.

Debugging

Message	When	Definition
`XMLHttpRequest proxied`	After wrapping XMLHttpRequest	XHR calls are intercepted.
`Needle found in XHR response`	Matching needle found	We will look for the search parameter next.
`Needle not found in XHR response`	Needle not found	Response will not be modified.
`Search * replaced with replacement in XHR response`	After replacement	The response was successfully replaced.
`Invalid JSONPath query: <<search>>`	Right after the snippet fires	The query could not be compiled, so the rule is not registered.
`JSONPath match at [<<key>>], replaced with <<replacement>>`	JSONPath mode, per matched property	A property matched the query and was replaced. One message per match.
`JSONPath: skipping non-JSON response or evaluation error: <<message>>`	Response could not be handled	The response was not valid JSON, or the query threw. The response is left untouched.