Location Guard by Kostas Chatzikokolakis, Marco Stronati

Modern browsers such as Mozilla Firefox can tell websites where you're located in order to provide location-aware functionality. Your geographic location is obtained through various means (eg. using wifi data) and is often highly accurate, which can be a violation of your privacy.

This extension allows you to enjoy the useful applications of geolocation while protecting your privacy. It does so by reporting a fake location to websites, obtained by adding a certain amount of "noise" to the real location. The noise is randomly selected in a way that ensures that the real location cannot be inferred with high accuracy.

Three configurable privacy levels are provided. The higher the privacy level the greater the amount of noise, which gives better privacy at the expense of a less accurate fake location. This can be configured per-website for flexibility: a more accurate location can be provided for driving directions than for a weather forecast. There's also an option to use a fixed location, instead of adding noise to the real one. This offers the best privacy (no dependence on the real location at all), at the cost of very low accuracy.

Note: your location can be also detected from your IP address, but usually with poor accuracy. Location Guard protects the accurate location revealed through the javascript API.