User-Agent
==========

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
------


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


Common format for web browsers:


```http
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:geckoversion) Gecko/geckotrail Firefox/firefoxversion
```


1. `Mozilla/5.0` is the general token that says that the browser is Mozilla-compatible. For historical reasons, almost every browser today sends it.
2. ***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.
3. **rv:*geckoversion*** indicates the release version of Gecko (such as "*17.0*"). In recent browsers, ***geckoversion*** is the same as ***firefoxversion***.
4. ***Gecko/geckotrail*** indicates that the browser is based on Gecko. (On the desktop, ***geckotrail*** is always the fixed string `20100101`.)
5. ***Firefox/firefoxversion*** 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; +http://www.google.com/bot.html)
```


```
Mozilla/5.0 (compatible; YandexAccessibilityBot/3.0; +http://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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See also
--------

* User-Agent detection, history and checklist
* Firefox user agent string reference
* Browser detection using the user agent
* Client hints