---
title: webRequest
slug: Mozilla/Add-ons/WebExtensions/API/webRequest
tags:
  - API
  - Add-ons
  - Extensions
  - Interface
  - NeedsTranslation
  - Non-standard
  - Reference
  - TopicStub
  - WebExtensions
  - webRequest
translation_of: Mozilla/Add-ons/WebExtensions/API/webRequest
---
<div>{{AddonSidebar}}</div>

<div>为发出的HTTP请求在不同阶段添加事件监听器。事件监听器可以接收到请求的详细信息，也可以修改或取消请求。</div>

<h2 id="概况">概况</h2>

<p>每个事件都会在请求的特定阶段触发。事件的顺序大概是这样的：</p>

<p>在请求过程中的任意时间，{{WebExtAPIRef("webRequest.onErrorOccurred", "onErrorOccurred")}} 可以被触发。虽然有时候触发的事件顺序不同，举个例子，在火狐浏览器中的HSTS过程，在onBeforeRequest事件执行后，onBeforeRedirect 事件会被立即触发。</p>

<p>所有的事件，接受<code>onErrorOccurred事件</code>, <code>addListener()</code>有三个参数 :</p>

<ul>
 <li>监听本身</li>
 <li>一个{{WebExtAPIRef("webRequest.RequestFilter", "filter")}} 对象, 所以你仅可以被特定请求或特定的资源类型提醒</li>
 <li>一个可选的<code>extraInfoSpec</code>对象. 你可以使用这个对象添加特定的事件命令</li>
</ul>

<p>这个监听函数接收一个<code>details</code>对象，这个对象包含这个请求的信息。他包含一个请求ID, 在插件中这个ID可以关联唯一个请求事件. 这个ID是浏览器会话和插件上下文中唯一的。他始终在同一个请求中，贯穿着转发和授权等事件中。</p>

<p>在一个给定的主机上使用webRequest API, 你必须有这个主机的相关权限，包括"webRequest" <a href="/en-US/Add-ons/WebExtensions/manifest.json/permissions#API_permissions">API permission</a> 和 <a href="/en-US/Add-ons/WebExtensions/manifest.json/permissions#Host_permissions">host permission</a>. 为了使用 "blocking" 特性，你必须有 "webRequestBlocking" API 权限。</p>

<p>这个webRequest API不能让你进入一些安全敏感的请求，比如<a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1279371">update checks and OCSP checks</a>.</p>

<h3 id="Modifying_requests">Modifying requests</h3>

<p>在下边这些事件中，你可以修改请求. 比如一些特别的操作:</p>

<ul>
 <li>取消请求:
  <ul>
   <li>{{WebExtAPIRef("webRequest.onBeforeRequest", "onBeforeRequest")}}</li>
   <li>{{WebExtAPIRef("webRequest.onBeforeSendHeaders", "onBeforeSendHeaders")}}</li>
   <li>{{WebExtAPIRef("webRequest.onAuthRequired", "onAuthRequired")}}</li>
  </ul>
 </li>
 <li>重定向请求:
  <ul>
   <li>{{WebExtAPIRef("webRequest.onBeforeRequest", "onBeforeRequest")}}</li>
   <li>{{WebExtAPIRef("webRequest.onHeadersReceived", "onHeadersReceived")}}</li>
  </ul>
 </li>
 <li>修改请求头:
  <ul>
   <li>{{WebExtAPIRef("webRequest.onBeforeSendHeaders", "onBeforeSendHeaders")}}</li>
  </ul>
 </li>
 <li>修改响应头:
  <ul>
   <li>{{WebExtAPIRef("webRequest.onHeadersReceived", "onHeadersReceived")}}</li>
  </ul>
 </li>
 <li>加入认证功能:
  <ul>
   <li>{{WebExtAPIRef("webRequest.onAuthRequired", "onAuthRequired")}}</li>
  </ul>
 </li>
</ul>

<p>为了完成这些操作，你需要在<code>extraInfoSpec</code>参数中添加"blocking"的值到事件的<code>addListener()</code>。这将使得监听器变成同步执行。在监听器中，你可以返回一个表明需要作修改的{{WebExtAPIRef("webRequest.BlockingResponse", "BlockingResponse")}}对象：比如说，你想要发送的修改后的请求头。</p>

<p>从Firefox 52开始，监听器会返回一个<code>resolve(BlockingResponse)</code> 的 <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise">Promise</a></code>，而不是直接返回一个<code>BlockingResponse</code>。这使得监听器可以异步地处理请求。</p>

<h2 id="Types">Types</h2>

<dl>
 <dt>{{WebExtAPIRef("webRequest.ResourceType")}}</dt>
 <dd>Represents a particular kind of resource fetched in a web request.</dd>
 <dt>{{WebExtAPIRef("webRequest.RequestFilter")}}</dt>
 <dd>An object describing filters to apply to webRequest events.</dd>
 <dt>{{WebExtAPIRef("webRequest.HttpHeaders")}}</dt>
 <dd>An array of HTTP headers. Each header is represented as an object with two properties: <code>name</code> and either <code>value</code> or <code>binaryValue</code>.</dd>
 <dt>{{WebExtAPIRef("webRequest.BlockingResponse")}}</dt>
 <dd>
 <p>An object of this type is returned by event listeners that have set <code>"blocking"</code> in their <code>extraInfoSpec</code> argument. By setting particular properties in <code>BlockingResponse</code>, the listener can modify network requests.</p>
 </dd>
 <dt>{{WebExtAPIRef("webRequest.UploadData")}}</dt>
 <dd>Contains data uploaded in a URL request.</dd>
</dl>

<h2 id="Properties">Properties</h2>

<dl>
 <dt>{{WebExtAPIRef("webRequest.MAX_HANDLER_BEHAVIOR_CHANGED_CALLS_PER_10_MINUTES")}}</dt>
 <dd>The maximum number of times that <code><a href="https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/WebRequest/handlerBehaviorChanged" title="Suppose an add-on's job is to block web requests against a pattern, and the following scenario happens:"><code>handlerBehaviorChanged()</code></a></code> can be called in a 10 minute period.</dd>
</dl>

<h2 id="Functions">Functions</h2>

<dl>
 <dt>{{WebExtAPIRef("webRequest.handlerBehaviorChanged()")}}</dt>
 <dd>This function can be used to ensure that event listeners are applied correctly when pages are in the browser's in-memory cache.</dd>
</dl>

<h2 id="Events">Events</h2>

<dl>
 <dt>{{WebExtAPIRef("webRequest.onBeforeRequest")}}</dt>
 <dd>Fired when a request is about to be made, and before headers are available. This is a good place to listen if you want to cancel or redirect the request.</dd>
 <dt>{{WebExtAPIRef("webRequest.onBeforeSendHeaders")}}</dt>
 <dd>Fired before sending any HTTP data, but after HTTP headers are available. This is a good place to listen if you want to modify HTTP request headers.</dd>
 <dt>{{WebExtAPIRef("webRequest.onSendHeaders")}}</dt>
 <dd>Fired just before sending headers. If your add-on or some other add-on modified headers in <code>{{WebExtAPIRef("webRequest.onBeforeSendHeaders", "onBeforeSendHeaders")}}</code>, you'll see the modified version here.</dd>
 <dt>{{WebExtAPIRef("webRequest.onHeadersReceived")}}</dt>
 <dd>Fired when the HTTP response headers associated with a request have been received. You can use this event to modify HTTP response headers.</dd>
 <dt>{{WebExtAPIRef("webRequest.onAuthRequired")}}</dt>
 <dd>Fired when the server asks the client to provide authentication credentials. The listener can do nothing, cancel the request, or supply authentication credentials.</dd>
 <dt>{{WebExtAPIRef("webRequest.onResponseStarted")}}</dt>
 <dd>Fired when the first byte of the response body is received. For HTTP requests, this means that the status line and response headers are available.</dd>
 <dt>{{WebExtAPIRef("webRequest.onBeforeRedirect")}}</dt>
 <dd>Fired when a server-initiated redirect is about to occur.</dd>
 <dt>{{WebExtAPIRef("webRequest.onCompleted")}}</dt>
 <dd>Fired when a request is completed.</dd>
 <dt>{{WebExtAPIRef("webRequest.onErrorOccurred")}}</dt>
 <dd>Fired when an error occurs.</dd>
</dl>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p>{{Compat("webextensions.api.webRequest")}}</p>

<div class="hidden note">
<p>The "Chrome incompatibilities" section is included from <a href="https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Chrome_incompatibilities"> https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Chrome_incompatibilities</a> using the <a href="/en-US/docs/Template:WebExtChromeCompat">WebExtChromeCompat</a> macro.</p>

<p>If you need to update this content, edit <a href="https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Chrome_incompatibilities">https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Chrome_incompatibilities</a>, then shift-refresh this page to see your changes.</p>
</div>

<h3 id="Edge_incompatibilities">Edge incompatibilities</h3>

<p>Promises are not supported in Edge. Use callbacks instead.</p>

<p>{{Compat("webextensions.api.webRequest")}} {{WebExtExamples("h2")}}</p>

<div class="note"><strong>Acknowledgements</strong>

<p>This API is based on Chromium's <a href="https://developer.chrome.com/extensions/webRequest"><code>chrome.webRequest</code></a> API. This documentation is derived from <a href="https://chromium.googlesource.com/chromium/src/+/master/extensions/common/api/web_request.json"><code>web_request.json</code></a> in the Chromium code.</p>

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

<div class="hidden">
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