declarativeNetRequest.ModifyHeaderInfo

The request or response header to modify for a request, declared in the rule.action.requestHeaders array or rule.action.responseHeaders array for rules whose rule.action.type is "modifyHeaders".

Each object describes one header modification. To modify multiple headers, multiple objects can be specified in these arrays, or across multiple rules.

Matching modifyHeaders rules are applied in the order described at Matching precedents. Within each extension, all modifyHeaders rules with a priority lower than or equal to matching allow or allowAllRequests rules are ignored.

If multiple modifyHeaders rules specify the same header, the resulting modification for the header is determined based on the priority of each rule and the operations specified:

• If a rule has been appended to a header, then lower-priority rules can only append to that header. set and remove operations are not permitted.
• If a rule has set a header, lower priority rules cannot modify the header except for append rules from the same extension.
• If a rule has removed a header, lower priority rules cannot modify the header.