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(
  listener,             // function
  filter,               //  object
  extraInfoSpec         //  optional array of strings
)
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.
originUrl
string. URL of the resource that triggered this request. Note that this may not be the same as the URL of the page into which the requested resource will be loaded. For example, if a document triggers a load in a different window through the target attribute of a link, or a CSS document includes an image using the url() functional notation, then this will be the URL of the original document or of the CSS document, respectively.
requestHeadersOptional
webRequest.HttpHeaders. The HTTP request headers that have been sent out with this request.

Browser compatibility

Chrome Edge Firefox Firefox for Android Opera
Basic support Yes Yes 45.0 48.0 33

Compatibility notes

Chrome

  • 'originUrl' is not supported.

Firefox

  • 'originUrl' is supported from version 48.

Opera

  • 'originUrl' is not supported.

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
browser.webRequest.onSendHeaders.addListener(
  logCookies,
  {urls: [targetPage]},
  ["requestHeaders"]
);

Acknowledgements

This API is based on Chromium's chrome.webRequest API. This documentation is derived from web_request.json in the Chromium code.

Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.

Document Tags and Contributors

 Contributors to this page: wbamberg, Makyen
 Last updated by: wbamberg,