Mozilla Firefox is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, Mozilla Corporation. It was first released in 2004 and is available for Windows, macOS, Linux, iOS, and Android.

Firefox is known for its emphasis on privacy and security. The browser includes features such as tracker blocking, password management, and a private browsing mode that does not save any browsing history or cookies. Firefox also supports Do Not Track, a privacy feature that asks websites not to track a user's browsing activity.

In addition to its privacy features, Firefox is known for its customizability. Users can customize the browser's appearance and functionality using a wide range of add-ons and extensions, which can be downloaded from the Firefox Add-ons marketplace. Firefox also supports a variety of web standards, including HTML5, CSS, and JavaScript, making it compatible with many modern websites and web applications.

Firefox also offers a variety of features aimed at enhancing the user experience, such as tabbed browsing, spell checking, and automatic updates. The browser also includes a built-in search bar that can be customized to use a variety of search engines.

Overall, Firefox is a popular and versatile web browser that emphasizes privacy, security, and customizability. It is widely used by individuals and organizations of all sizes and has become an essential tool for browsing the web.