webRequest.onSendHeaders

This event is fired just before sending headers. If your extension or some other extension 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

cookieStoreId
string. If the request is from a tab open in a contextual identity, the cookie store ID of the contextual identity.
documentUrl
string. URL of the document in which the resource will be loaded. For example, if the web page at "https://example.com" contains an image or an iframe, then the documentUrl for the image or iframe will be "https://example.com". For a top-level document, documentUrl is undefined.
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
incognito
boolean. Whether the request is from a private browsing window.
method
string. Standard HTTP method: for example, "GET" or "POST".
originUrl

string. URL of the resource which triggered the request. For example, if "https://example.com" contains a link, and the user clicks the link, then the originUrl for the resulting request is "https://example.com".

The originUrl is often but not always the same as the documentUrl. For example, if a page contains an iframe, and the iframe contains a link that loads a new document into the iframe, then the documentUrl for the resulting request will be the iframe's parent document, but the originUrl will be the URL of the document in the iframe that contained the link.

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

object. This property is present only if the request is being proxied. It contains the following properties:

host
string. The hostname of the proxy server.
port
integer. The port number of the proxy server.
type

string. The type of proxy server. One of:

  • "http": HTTP proxy (or SSL CONNECT for HTTPS)
  • "https": HTTP proxying over TLS connection to proxy
  • "socks": SOCKS v5 proxy
  • "socks4": SOCKS v4 proxy
  • "direct": no proxy
  • "unknown": unknown proxy
username
string. Username for the proxy service.
proxyDNS
boolean. True if the proxy will perform domain name resolution based on the hostname supplied, meaning that the client should not do its own DNS lookup.
failoverTimeout
integer. Failover timeout in seconds. If the proxy connection fails, the proxy will not be used again for this period.
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.
requestHeadersOptional
webRequest.HttpHeaders. The HTTP request headers that have been sent out with this request.
tabId
integer. ID of the tab in which the request takes place. Set to -1 if the request isn't related to a tab.
thirdParty
boolean. Indicates whether the request and its content window hierarchy are third party.
timeStamp
number. The time when this event fired, in milliseconds since the epoch.
type
webRequest.ResourceType. The type of resource being requested: for example, "image", "script", "stylesheet".
url
string. Target of the request.
urlClassification
object. The type of tracking associated with the request, if with the request has been classified by Firefox Tracking Protection. This is an object with the following properties:
firstParty
array of strings. Classification flags for the request's first party.
thirdParty
array of strings. Classification flags for the request or its window hierarchy's third parties.
The classification flags include:
  • fingerprinting and fingerprinting_content: indicates the request is involved in fingerprinting. fingerprinting_content indicates the request is loaded from an origin that has been found to fingerprint but is not considered to participate in tracking, such as a payment provider.
  • cryptomining and cryptomining_content: similar to the fingerprinting category but for cryptomining resources.
  • tracking, tracking_ad, tracking_analytics, tracking_social,  and tracking_content: indicates the request is involved in tracking. tracking is any generic tracking request, the ad, analytics, social, and content suffixes identify the type of tracker.
  • any_basic_tracking: a meta flag that combines any tracking and fingerprinting flags, excluding tracking_content and fingerprinting_content.
  • any_strict_tracking: a meta flag that combines any tracking and fingerprinting flags, including tracking_content and fingerprinting_content.
  • any_social_tracking: a meta flag that combines any social tracking flags.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxOperaSafariFirefox for Android
onSendHeadersChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14
Notes
Full support 14
Notes
Notes extraInfoSpec options are not supported.
Firefox Android Full support 48
details.cookieStoreIdChrome No support NoEdge No support NoFirefox Full support 68Opera No support NoSafari No support NoFirefox Android No support No
details.documentUrlChrome No support NoEdge No support NoFirefox Full support 54Opera No support NoSafari No support NoFirefox Android Full support 54
details.frameIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.incognitoChrome No support NoEdge No support NoFirefox Full support 68Opera No support NoSafari No support NoFirefox Android No support No
details.methodChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.originUrlChrome No support NoEdge No support NoFirefox Full support 48Opera No support NoSafari No support NoFirefox Android Full support 48
details.parentFrameIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.proxyInfoChrome No support NoEdge No support NoFirefox Full support 57Opera No support NoSafari No support NoFirefox Android Full support 57
details.requestIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.requestHeadersChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.tabIdChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.thirdPartyChrome No support NoEdge No support NoFirefox Full support 72Opera No support NoSafari No support NoFirefox Android No support No
details.timeStampChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.typeChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.urlChrome Full support YesEdge Full support 14Firefox Full support 45Opera Full support YesSafari Full support 14Firefox Android Full support 48
details.urlClassificationChrome No support NoEdge No support NoFirefox Full support 74Opera No support NoSafari No support NoFirefox Android No support No

Legend

Full support  
Full support
No support  
No support
See implementation notes.
See implementation notes.

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.