"Perhaps a better resource: Geolocation in Firefox (by Mozilla) TLDR: no gps is being used How does it work?
When you visit a location-aware website, Firefox will ask you if you want to share your location. If you consent, Firefox gathers information about nearby wireless access points and your computer’s IP address. Then Firefox sends this information to the default geolocation service provider, Google Location Services, to get an estimate of your location. That location estimate is then shared with the requesting website. If you say that you do not consent, Firefox will not do anything.
How accurate are the locations?
Accuracy varies greatly from location to location. In some places, our service providers may be able to provide a location to within a few meters. However, in other areas it might be much more than that. All locations returned by our service providers are estimates only and we do not guarantee the accuracy of the locations provided. Please do not use this information for emergencies. Always use common sense.
What information is being sent, and to whom? How is my privacy protected?
Your privacy is extremely important to us, and Firefox never shares your location without your permission. When you visit a page that requests your information, you’ll be asked before any information is shared with the requesting website and our third-party service provider. By default, Firefox uses Google Location Services to determine your location by sending:
your computer’s IP address, information about the nearby wireless access points, and a random client identifier, which is assigned by Google, that expires every 2 weeks."