Which Mozilla web browser was first released in 2004?

Firefox was the Mozilla web browser first released in 2004.

Mozilla released Firefox 1.0 on November 9, 2004. The browser grew from an earlier standalone Mozilla project whose first public release was called Phoenix in 2002; trademark concerns led to the name Firebird, and it was eventually renamed Firefox. The 1.0 launch made Firefox available for Windows, Mac OS X, and Linux.

Firefox was designed as a free, open-source browser with a strong focus on security, customization, and user control. Features such as pop-up blocking, tabbed browsing, themes, and extensions helped it stand out during a period when Internet Explorer dominated desktop browsing. Its rendering engine was Gecko, developed within the Mozilla project.

The date can cause confusion because Phoenix and later preview builds appeared before the Firefox 1.0 release. Conversely, Vivaldi and Brave launched much later, while Opera dates to the 1990s. The question refers to the browser’s Firefox-branded release, not the project’s earlier names.