Revision 1095831 of User-Agent

  • Revision slug: Web/HTTP/Headers/User-Agent
  • Revision title: User-Agent
  • Revision id: 1095831
  • Created:
  • Creator: fscholz
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{{HTTPSidebar}}

The User-Agent request header contains a characteristic string that allows the network protocol to identify the application type, operating system, software vendor or software version of the requesting software user agent.

Please read Browser detection using the user agent and why Serving different Web pages or services to different browsers is usually a bad idea.

Header type {{Glossary("Request header")}}
{{Glossary("Forbidden header name")}} no

Syntax

User-Agent: <product> / <product-version> <comment>

Common format for web browsers:

User-Agent: Mozilla/<version> (<system-information>) <platform> (<platform-details>) <extensions>

Directives

<product>
A product identifier
<product-version>
A version number of the product.
<comment>
Zero or more comments containing sub product information, for example.

Firefox UA string

The UA string of Firefox itself is broken down into four components:

Mozilla/5.0 (platform; rv:geckoversion) Gecko/geckotrail Firefox/firefoxversion

  • Mozilla/5.0 is the general token that says the browser is Mozilla compatible, and is common to almost every browser today.
  • platform describes the native platform the browser is running on (e.g. Windows, Mac, Linux or Android), and whether or not it's a mobile phone. Firefox OS phones simply say "Mobile"; the web is the platform. Note that platform can consist of multiple "; "-separated tokens. See below for further details and examples.
  • rv:geckoversion indicates the release version of Gecko (such as "17.0"). In recent browsers, geckoversion is the same as firefoxversion.
  • Gecko/geckotrail indicates that the browser is based on Gecko.
  • On Desktop, geckotrail is the fixed string "20100101"
  • Firefox/firefoxversion indicates 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

For more details on Firefox and Gecko based user agent strings, see the Firefox user agent string reference.

Chrome UA string

The Chrome (or Chromium/blink-based engines) user agent string is similar to the Firefox format. 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, 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

Safari UA string

In this example, the user agent string is mobile safari version. It contains the word "Mobile".

Examples

Mozilla/5.0 (Linux; U; Android 4.0.3; de-ch; HTC Sensation Build/IML74K) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30

Specifications

Specification Title
{{RFC("7231", "User-Agent", "5.5.3")}} Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content

Browser compatibility

{{Compat}}

See also

Revision Source

<div>{{HTTPSidebar}}</div>

<p>The <strong>User-Agent</strong> request header contains a characteristic string that allows the network protocol to identify the application type, operating system, software vendor or software version of the requesting software user agent.</p>

<div class="note">
<p>Please read <a href="/en-US/docs/Web/HTTP/Browser_detection_using_the_user_agent">Browser detection using the user agent</a> and why Serving different Web pages or services to different browsers is usually a bad idea.</p>
</div>

<table class="properties">
 <tbody>
  <tr>
   <th scope="row">Header type</th>
   <td>{{Glossary("Request header")}}</td>
  </tr>
  <tr>
   <th scope="row">{{Glossary("Forbidden header name")}}</th>
   <td>no</td>
  </tr>
 </tbody>
</table>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox">
User-Agent: &lt;product&gt; / &lt;product-version&gt; &lt;comment&gt;

Common format for web browsers:

User-Agent: Mozilla/&lt;version&gt; (&lt;system-information&gt;) &lt;platform&gt; (&lt;platform-details&gt;) &lt;extensions&gt;
</pre>

<h2 id="Directives">Directives</h2>

<dl>
 <dt>&lt;product&gt;</dt>
 <dd>A product identifier</dd>
 <dt>&lt;product-version&gt;</dt>
 <dd>A version number of the product.</dd>
 <dt>&lt;comment&gt;</dt>
 <dd>Zero or more comments containing sub product information, for example.</dd>
</dl>

<h2 id="Firefox_UA_string">Firefox UA string</h2>

<p>The UA&nbsp;string of Firefox itself is broken down into four components:</p>

<p><strong>Mozilla/5.0 (<em>platform</em>; rv:<em>geckoversion</em>) Gecko/<em>geckotrail</em> Firefox/<em>firefoxversion</em></strong></p>

<ul>
 <li><em><strong>Mozilla/5.0</strong></em> is the general token that says the browser is Mozilla compatible, and is common to almost every browser today.</li>
 <li><strong><em>platform</em></strong> describes the native platform the browser is running on (e.g. Windows, Mac, Linux or Android), and whether or not it's a mobile phone. Firefox OS phones simply say "Mobile"; the web is the platform. Note that <strong><em>platform</em></strong> can consist of multiple "; "-separated tokens. See below for further details and examples.</li>
 <li><strong>rv:<em>geckoversion</em></strong> indicates the release version of Gecko (such as <em>"17.0"</em>). In recent browsers, <strong><em>geckoversion</em></strong> is the same as <strong><em>firefoxversion</em></strong>.</li>
 <li><strong><em>Gecko/geckotrail</em></strong> indicates that the browser is based on Gecko.</li>
 <li>On Desktop, <em><strong>geckotrail</strong></em> is the fixed string "20100101"</li>
 <li><em><strong>Firefox/firefoxversion</strong></em> indicates the browser is Firefox, and provides the version (such as "<em>17.0"</em>).</li>
</ul>

<h3 id="Examples">Examples</h3>

<pre>
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:47.0) Gecko/20100101 Firefox/47.0
Mozilla/5.0 (Macintosh; Intel Mac OS&nbsp;X&nbsp;<em>x.y</em>; rv:42.0) Gecko/20100101 Firefox/42.0
</pre>

<p>For more details on Firefox and Gecko based user agent strings, see the <a href="/en-US/docs/Web/HTTP/Headers/User-Agent/Firefox">Firefox user agent string reference</a>.</p>

<h2 id="Chrome_UA_string">Chrome UA string</h2>

<p>The Chrome (or Chromium/blink-based engines) user agent string is similar to the Firefox format. For compatibility, it adds strings like "KHTML, like Gecko" and "Safari".</p>

<h3 id="Examples_2">Examples</h3>

<pre>
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36</pre>

<h2 id="Opera_UA_string">Opera UA string</h2>

<p>The Opera browser is also based on the blink engine, which is why it almost looks the same, but adds "OPR/&lt;version&gt;".</p>

<h3 id="Examples_3">Examples</h3>

<pre>
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</pre>

<h2 id="Safari_UA_string">Safari UA string</h2>

<p>In this example, the user agent string is mobile safari version. It contains the word "Mobile".</p>

<h3 id="Examples_4">Examples</h3>

<pre>
Mozilla/5.0 (Linux; U; Android 4.0.3; de-ch; HTC Sensation Build/IML74K) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Title</th>
  </tr>
  <tr>
   <td>{{RFC("7231", "User-Agent", "5.5.3")}}</td>
   <td>Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content</td>
  </tr>
 </tbody>
</table>

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

<p class="hidden">The compatibility table in this page is generated from structured data. If you’d like to contribute to the data, please check out <a href="https://github.com/mdn/browser-compat-data/README.md">https://github.com/mdn/browser-compat-data/README.md</a> and send us a pull request.</p>

<p>{{Compat}}</p>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="https://hacks.mozilla.org/2013/09/user-agent-detection-history-and-checklist/">User-Agent detection, history and checklist</a></li>
 <li><a href="/en-US/docs/Web/HTTP/Headers/User-Agent/Firefox">Firefox user agent string reference</a></li>
 <li>
  <p><a href="/en-US/docs/Web/HTTP/Browser_detection_using_the_user_agent">Browser detection using the user agent</a></p>
 </li>
</ul>
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