Firefox is the third most popular web browser in the world, with a market share of about 7%. It is particularly popular among users who value privacy and security. Firefox is based on the Gecko rendering engine, which is also used by other web browsers such as Thunderbird and SeaMonkey. Firefox is supported by a large community of volunteers who help to develop and test the browser. Firefox is a non-profit project, which means that it is not beholden to the interests of any shareholders. This allows Firefox to focus on what is best for its users.