Early beginnings: a pared-down browser

Phoenix 0.1, the first official release
Phoenix 0.1, the first official release
Firefox 1.0, the first release targeted for general public
Firefox 1.0, the first release targeted for general public

Hyatt and Ross' mozilla/browser (later Phoenix, Firebird and finally Firefox) browser was created to combat the perceived software bloat of the Mozilla Suite (codenamed, internally referred to, and continued by the community as SeaMonkey), which integrated features such as IRC, mail and news, and WYSIWYG HTML editing into one software suite.

Firefox retains the cross-platform nature of the original Mozilla browser, using the XUL user interface markup language. The use of XUL makes it possible to extend the browser's capabilities through the use of extensions and themes. The development and installation processes of these add-ons raised security concerns, and with the release of Firefox 0.9, the Mozilla Foundation opened a Mozilla Update website containing "approved" themes and extensions. The use of XUL sets Firefox apart from other browsers, including other projects based on Mozilla's Gecko layout engine and most other browsers, which use interfaces native to their respective platforms (Galeon and Epiphany use GTK+; K-Meleon uses MFC; and Camino uses Cocoa). Many of these projects were started before Firefox, and probably served as inspiration.

The first sign of a Firefox-like project was a small application sample (presumably to demonstrate how to embed Gecko in another application) shipped with early milestone builds of Mozilla. Featuring only "back", "forward", and "stop" buttons and a URL field (no cache, no stored history, etc.), it was minimalistic and thus a lot lighter than Mozilla itself. Eventually, it was no longer shipped with Mozilla's binary builds.

Although the Mozilla Foundation had intended to make the Mozilla Suite obsolete and to replace it with Firefox, the Foundation continued to maintain the suite until April 12, 2006[1] because it had many corporate users, as well as being bundled with other software. The Mozilla community (as opposed to the Foundation) continues to release new versions of the suite using the product name SeaMonkey to avoid any possible confusion with the original Mozilla Suite.

On February 5, 2004 the business and IT consulting company AMS categorized Mozilla Firefox (then Firebird) as a "Tier 1" (meaning "Best of Breed") open source product (Keating, 2004). This meant that AMS considered Firebird (as it was called at the time) to be virtually risk-free and technically strong.