This event is triggered before sending any HTTP data, but after all HTTP headers are available. This is a good place to listen if you want to modify HTTP request headers.
To have the request headers passed into the listener along with the rest of the request data, pass
"requestHeaders"
在
extraInfoSpec
数组。
To modify the headers synchronously: pass
"blocking"
in
extraInfoSpec
, then in your event listener, return a
BlockingResponse
with a property named
requestHeaders
, whose value is the set of request headers to send.
To modify the headers asynchronously: pass
"blocking"
in
extraInfoSpec
, then in your event listener, return a
Promise
which is resolved with a
BlockingResponse
.
若使用
"blocking"
, you must have the
"webRequestBlocking" API permission
in your manifest.json.
It is possible for extensions to conflict here. If two extensions listen to
onBeforeSendHeaders
for the same request, then the second listener will see modifications made by the first listener, and will be able to undo any changes made by the first listener. For example, if the first listener adds a
Cookie
header, and the second listener strips all
Cookie
headers, then the first listener's modifications will be lost. If you want to see the headers that are actually sent, without the risk that another extension will subsequently alter them, use
onSendHeaders
, although you can't modify headers on this event.
Not all headers actually sent are always included in
requestHeaders
. In particular, headers related to caching (for example,
Cache-Control
,
If-Modified-Since
,
If-None-Match
) are never sent. Also, behavior here may differ across browsers.
According to the specification, header names are case-insensitive. This means that be to sure of matching a particular header, the listener should lowercase the name before comparing it:
for (let header of e.requestHeaders) {
if (header.name.toLowerCase() === desiredHeader) {
// process header
}
}
The browser preserves the original case of the header name as generated by the browser. If the extension's listener changes the case, this change will not be kept.
browser.webRequest.onBeforeSendHeaders.addListener(
listener, // function
filter, // object
extraInfoSpec // optional array of strings
)
browser.webRequest.onBeforeSendHeaders.removeListener(listener)
browser.webRequest.onBeforeSendHeaders.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)
校验是否
listener
is registered for this event. Returns
true
if it is listening,
false
否则。
callback
Function that will be called when this event occurs. The function will be passed the following arguments:
details
对象
. Details of the request. This will include request headers if you have included
"requestHeaders"
in
extraInfoSpec
.
返回：
webRequest.BlockingResponse
。若
"blocking"
is specified in the
extraInfoSpec
parameter, the event listener should return a
BlockingResponse
object, and can set its
requestHeaders
特性。
filter
webRequest.RequestFilter
. A set of filters that restricts the events that will be sent to this listener.
extraInfoSpec
可选
array
of
string
. Extra options for the event. You can pass any of the following values:
"blocking"
: make the request synchronous, so you can modify request headers
"requestHeaders"
: include the request headers in the
details
object passed to the listener
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.
方法
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".
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
对象
. 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:
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.
requestHeaders
可选
webRequest.HttpHeaders
. The HTTP request headers that will be sent with this request.
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.
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
编号
. 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
对象
. 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
，和
tracking_content
: indicates the request is involved in tracking.
tracking
is any generic tracking request, the
ad
,
analytics
,
social
，和
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.
BCD tables only load in the browser
This code changes the "User-Agent" header so the browser identifies itself as Opera 12.16, but only when visiting pages under https://httpbin.org/".
"use strict";
/*
This is the page for which we want to rewrite the User-Agent header.
*/
var targetPage = "https://httpbin.org/*";
/*
Set UA string to Opera 12
*/
var ua = "Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16";
/*
Rewrite the User-Agent header to "ua".
*/
function rewriteUserAgentHeader(e) {
for (var header of e.requestHeaders) {
if (header.name.toLowerCase() === "user-agent") {
header.value = ua;
}
}
return {requestHeaders: e.requestHeaders};
}
/*
Add rewriteUserAgentHeader as a listener to onBeforeSendHeaders,
only for the target page.
Make it "blocking" so we can modify the headers.
*/
browser.webRequest.onBeforeSendHeaders.addListener(
rewriteUserAgentHeader,
{urls: [targetPage]},
["blocking", "requestHeaders"]
);
This code is exactly like the previous example, except that the listener is asynchronous, returning a
Promise
which is resolved with the new headers:
"use strict";
/*
This is the page for which we want to rewrite the User-Agent header.
*/
var targetPage = "https://httpbin.org/*";
/*
Set UA string to Opera 12
*/
var ua = "Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16";
/*
Rewrite the User-Agent header to "ua".
*/
function rewriteUserAgentHeaderAsync(e) {
var asyncRewrite = new Promise((resolve, reject) => {
window.setTimeout(() => {
for (var header of e.requestHeaders) {
if (header.name.toLowerCase() === "user-agent") {
header.value = ua;
}
}
resolve({requestHeaders: e.requestHeaders});
}, 2000);
});
return asyncRewrite;
}
/*
Add rewriteUserAgentHeader as a listener to onBeforeSendHeaders,
only for the target page.
Make it "blocking" so we can modify the headers.
*/
browser.webRequest.onBeforeSendHeaders.addListener(
rewriteUserAgentHeaderAsync,
{urls: [targetPage]},
["blocking", "requestHeaders"]
);
注意：
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.
最后修改： , 由 MDN 贡献者