webRequest.onSendHeaders

This event is fired just before sending headers. If your add-on or some other add-on modified headers in onBeforeSendHeaders, you'll see the modified version here.

This event is informational only.

Syntax

browser.webRequest.onSendHeaders.addListener(function(
  details // object
) {...})
browser.webRequest.onSendHeaders.removeListener(listener)
browser.webRequest.onSendHeaders.hasListener(listener)

Events have three functions:

addListener(callback, filter, extraInfoSpec)

Adds a listener to this event.

removeListener(listener)

Stop listening to this event. The listener argument is the listener to remove.

hasListener(listener)

Check whether listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

callback

Function that will be called when this event occurs. The function will be passed the following arguments:

details

object. Details about the request. See details below.

filter

webRequest.RequestFilter. A filter that restricts the events that will be sent to this listener.

extraInfoSpecOptional

array of string. Extra options for the event. You can only pass one value here:

• "requestHeaders": include the request headers in the details object passed to the listener

Additional objects

details

requestId

string. The ID of the request. Request IDs are unique within a browser session, so you can use them to relate different events associated with the same request.

url

string. Target of the request.

method

string. Standard HTTP method: for example, "GET" or "POST".

frameId

integer. Zero if the request happens in the main frame; a positive value is the ID of a subframe in which the request happens. If the document of a (sub-)frame is loaded (type is main_frame or sub_frame), frameId indicates the ID of this frame, not the ID of the outer frame. Frame IDs are unique within a tab.

parentFrameId

integer. ID of the frame that contains the frame which sent the request. Set to -1 if no parent frame exists.

tabId

integer. ID of the tab in which the request takes place. Set to -1 if the request isn't related to a tab.

type

webRequest.ResourceType. The type of resource being requested: for example, "image", "script", "stylesheet".

timeStamp

number. The time when this event fired, in milliseconds since the epoch.

requestHeadersOptional

webRequest.HttpHeaders. The HTTP request headers that have been sent out with this request.

Browser compatibility

Examples

This code logs all cookies that will be sent in making requests to the target match pattern:

// The target match pattern
var targetPage = "*://*.google.ca/*";

// Log cookies sent with this request
function logCookies(e) {
  for (var header of e.requestHeaders) {
    if (header.name == "Cookie") {
      console.log(header.value);
    }
  }
}

// Listen for onSendHeaders, and pass
// "requestHeaders" so we get the headers
chrome.webRequest.onSendHeaders.addListener(
  logCookies,
  {urls: [targetPage]},
  ["requestHeaders"]
);

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