NavigatorID.userAgent

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NavigatorID.userAgent read-only property returns the user agent string for the current browser.

The specification asks browsers to provide as little information via this field as possible. Never assume that the value of this property will stay the same in future versions of the same browser. Try not to use it at all, or only for current and past versions of a browser. New browsers may start using the same UA, or part of it, as an older browser: you really have no guarantee that the browser agent is indeed the one advertised by this property.

Also keep in mind that users of a browser can change the value of this field if they want (UA spoofing).

Browser identification based on detecting the user agent string is unreliable and is not recommended , as the user agent string is user configurable. For example:

In Firefox, you can change the preference general.useragent.override in about:config . Some Firefox extensions do that; however, this only changes the HTTP header that gets sent, and doesn't affect browser detection performed by JavaScript code.
Opera 6+ allows users to set the browser identification string via a menu.
Microsoft Internet Explorer uses the Windows registry.
Safari and iCab allow users to change the browser user agent string to predefined Internet Explorer or Netscape strings via a menu.

句法

var ua = navigator.userAgent;

值

A DOMString specifying the complete user agent string the browser provides both in HTTP headers and in response to this and other related methods on the Navigator 对象。

The user agent string is built on a formal structure which can be decomposed into several pieces of info. Each of these pieces of info comes from other navigator properties which are also settable by the user. Gecko-based browsers comply with the following general structure:

userAgent = appCodeName/appVersion number (Platform; Security; OS-or-CPU;
Localization; rv: revision-version-number) product/productSub
Application-Name Application-Name-version

范例

alert(window.navigator.userAgent)
// alerts "Mozilla/5.0 (Windows; U; Win98; en-US; rv:0.9.2) Gecko/20010725 Netscape6/6.1"

规范

规范	状态	注释
HTML 实时标准 The definition of 'NavigatorID.userAgent' in that specification.	实时标准	初始定义

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	桌面						移动
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`userAgent`	Chrome Yes	Edge 12	Firefox Yes	IE Yes	Opera Yes	Safari Yes	WebView Android Yes	Chrome Android Yes	Firefox Android Yes	Opera Android Yes	Safari iOS Yes	Samsung Internet Android Yes

图例

完整支持

另请参阅

User-Agent HTTP header

元数据

最后修改： Aug 31, 2020

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句法

值

范例

规范

浏览器兼容性

图例

另请参阅

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