Mozilla Firefox is a free, open-source cross-platform web browser. Use this tag if your question is related to the inner workings of Firefox or if it relates to code that is not working on Firefox which does work in other browsers. Questions about Firefox add-on development should be tagged [firefox-addon]. If your question is about using Firefox for browsing (i.e. as an end user) you should ask your question on Super User instead.
Firefox is an open source, cross-platform web-browser created by Mozilla. It uses the open source gecko rendering engine and the spidermonkey JavaScript engine.
Standards
Firefox implements many web standards, including html4 (almost full html5), xml, xhtml, mathml, svg, css (with extensions), ecmascript (javascript), dom, xslt, xpath, and apng (Animated PNG) images with alpha transparency.
Platform availability
Firefox runs on various operating systems including windows, linux, mac, and freebsd, as well as on 
android, ios and firefox-os devices. Its source code is licensed under the Mozilla Public License.
There are various add-ons available for Firefox under various categories, such as web development, changing the appearance of Firefox and utilities such as download managers.
Resources
- List of all releases
- Firefox (Wikipedia)
- Firefox - Mozilla Wiki
- Support for Firefox
- Contributing to Firefox
- Working with Mozilla source code
- Firefox on MDN
What questions should have this tag?
Use this tag if your question is related to:
- Code that is not working on Firefox which does work in other browsers
- The inner workings of Firefox
Questions concerning Firefox add-on development should be tagged firefox-addon.
If your question is about using Firefox for browsing (i.e. as an end user) rather than the development of code for Firefox, you should ask your question on Super User instead.
Related tags
browser gecko spidermonkey 
google-chrome firefox-os internet-explorer
