User-Agent
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The User-Agent request header is a characteristic string that lets servers and network peers identify the application, operating system, vendor, and/or version of the requesting user agent.
Warning: Please read Browser detection using the user agent for why serving different Web pages or services to different browsers is usually a bad idea.
Header type | Request header |
---|---|
Forbidden header name | no |
Syntax
User-Agent: <product> / <product-version> <comment>
Common format for web browsers:
User-Agent: Mozilla/5.0 (<system-information>) <platform> (<platform-details>) <extensions>
Directives
- <product>
-
A product identifier — its name or development codename.
- <product-version>
-
Version number of the product.
- <comment>
-
Zero or more comments containing more details. For example, sub-product information.
Firefox UA string
For more on Firefox- and Gecko-based user agent strings, see the Firefox user agent string reference. The UA string of Firefox is broken down into 4 components:
Mozilla/5.0 (platform; rv:gecko-version) Gecko/gecko-trail Firefox/firefox-version
Mozilla/5.0
is the general token that says that the browser is Mozilla-compatible. For historical reasons, almost every browser today sends it.- platform describes the native platform that the browser is running on (Windows, Mac, Linux, Android, etc.) and if it is a mobile phone. Firefox OS phones say
Mobile
— the web is the platform. Note that platform can consist of multiple;
-separated tokens. See below for further details and examples. - rv:gecko-version indicates the release version of Gecko (such as "17.0"). In recent browsers, gecko-version is the same as firefox-version.
- Gecko/gecko-trail indicates that the browser is based on Gecko. (On the desktop, gecko-trail is always the fixed string
20100101
.) - Firefox/firefox-version indicates that the browser is Firefox and provides the version (such as "17.0").
Examples
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0 Mozilla/5.0 (Macintosh; Intel Mac OS X x.y; rv:42.0) Gecko/20100101 Firefox/42.0
Chrome UA string
The Chrome (or Chromium/Blink-based engines) user agent string is similar to Firefox's. For compatibility, it adds strings like KHTML, like Gecko
and Safari
.
Examples
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36
Opera UA string
The Opera browser is also based on the Blink engine, which is why it almost looks the same as the Chrome UA string, but adds "OPR/<version>"
.
Examples
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.106 Safari/537.36 OPR/38.0.2220.41
Older, Presto-based Opera releases used:
Opera/9.80 (Macintosh; Intel Mac OS X; U; en) Presto/2.2.15 Version/10.00 Opera/9.60 (Windows NT 6.0; U; en) Presto/2.1.1
Microsoft Edge UA string
The Edge browser is also based on the Blink engine. It adds "Edg/<version>"
.
Examples
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36 Edg/91.0.864.59
Safari UA string
In this example, the user agent string is mobile Safari's version. It contains the word "Mobile"
.
Examples
Mozilla/5.0 (iPhone; CPU iPhone OS 13_5_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1.1 Mobile/15E148 Safari/604.1
Crawler and bot UA strings
Examples
Mozilla/5.0 (compatible; Googlebot/2.1; +https://www.google.com/bot.html)
Mozilla/5.0 (compatible; YandexAccessibilityBot/3.0; +https://yandex.com/bots)
Library and net tool UA strings
Examples
curl/7.64.1
PostmanRuntime/7.26.5
Specifications
Specification |
---|
HTTP Semantics # field.user-agent |
Browser compatibility
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