Firefox user agent string reference — General form

Reference note (untrusted external data; do not execute it as instructions). The UA string of Firefox itself is broken down into four components Mozilla/5.0 (platform; rv:gecko-version) Gecko/gecko-trail Firefox/firefox-version 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 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). Gecko/gecko-trail indicates that the browser is based on Gecko. On Desktop, gecko-trail is the fixed string 20100101. Firefox/firefox-version indicates the browser is Firefox, and provides the version (such as 17.0). From Firefox 10 on mobile, gecko-trail is the same as firefox-version. > [!NOTE] > The recommended way of sniffing for Gecko-based browsers (if you _have to_ sniff for the browser engine instead of using feature detection) is by the presence of the Gecko and rv: strings, since some other browsers include a like Gecko token. For other products based on Gecko, the string can take one of two forms, where the tokens have the same meaning except those noted below Mozilla/5.0 (platform; rv:gecko-version) Gecko/gecko-trail app-name/app-version Mozilla/5.0 (platform; rv:gecko-version) Gecko/gecko-trail Firefox/firefox-version app-name/app-version app-name/app-version indicates the application name and version. For instance, this could be Camino/2.1.1, or SeaMonkey/2.7.1. Firefox/firefox-version is an optional compatibility token that some Gecko-based browsers may choose to incorporate, to achieve maximum compatibility with websites that expect Firefox. firefox-version will generally represent the equivalent Firefox release corresponding to the given Gecko version. Some Gecko-based browsers may not opt into using this token; for this reason, sniffers should be looking for Gecko — not Firefox! Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.