Gecko-based software

Instantbird is a cross-platform instant messaging client based on Mozilla's XULRunner and the open source library libpurple used in Pidgin.

Komodo Edit is a free text editor for dynamic programming languages.

Mozilla Sunbird was a free and open source, cross-platform calendar application that was developed by the Mozilla Foundation, Sun Microsystems and many volunteers.

SeaMonkey is a free and open-source Internet suite.

KompoZer is an open source WYSIWYG HTML editor based on the now-discontinued Nvu editor.

Songbird is a discontinued music player originally released in early 2006 with the stated mission "to incubate Songbird, the first Web player, to catalyze and champion a diverse, open Media Web".

Kazehakase (Japanese: Dr. Wind (風博士 kaze hakase) is a web browser for Unix-like operating systems that uses the GTK+ libraries. Kazehakase embeds the Gecko layout engine as well as GTK+ WebKit. However, the author also plans to add the ability to switch between additional different rendering engines (e.g. GtkHTML, Dillo, w3m). The browser is named after the short story "Kazehakase" by the Japanese author Ango Sakaguchi; its literal meaning is "Dr. Wind" (a PhD rather than a medical doctor). Kazehakase seems to be no longer in active development since 2012.

Galeon is a discontinued Gecko-based web browser that was created by Marco Pesenti Gritti with the goal of delivering a consistent browsing experience to GNOME desktop environment.

Firefox for Android (codenamed Fennec) is the build of the Mozilla Firefox web browser for devices such as smartphones and tablet computers.

Firefox OS (project name: Boot to Gecko, also known as B2G) is a discontinued open-source operating system – made for smartphones, tablet computers and smart TVs – designed by Mozilla and external contributors, based on the rendering engine of their Firefox web browser and the Linux kernel.

Camino (from the Spanish word camino meaning "path") is a discontinued free, open source, GUI-based Web browser based on Mozilla's Gecko layout engine and specifically designed for the OS X operating system.

It is designed to support open Internet standards, and is used by different applications to display web pages and, in some cases, an application's user interface itself (by rendering XUL).

Flock is a discontinued web browser that specialized in providing social networking and Web 2.

K-Meleon is an open-source web browser for Microsoft Windows.

TenFourFox is a web browser based on Mozilla's Gecko layout engine.

Goanna is a fork of the Netscape/Mozilla-sourced Gecko engine, and shares many of its features.

Classilla is a Gecko-based Internet suite for PowerPC-based classic Macintosh operating systems, essentially an updated descendant of the defunct Mozilla Application Suite by way of the Mac OS port maintained in the aborted WaMCom project.

GNU IceCat, formerly known as GNU IceWeasel, is a free software rebranding of the Mozilla Firefox web browser distributed by the GNU Project.

Komodo IDE is an integrated development environment (IDE) for dynamic programming languages.

Nightingale is a free, open source audio player and web browser based on the Songbird media player source code.

Spicebird was a personal information manager based on Mozilla Thunderbird's code developed by an Indian company called Synovel.