Orbit was a Firefox extension that used large language models to summarize emails, articles, videos, and more. When summarizing content, Orbit gathered and sent the context to an instance of the Mistral 7B LLM, hosted by Mozilla on GCP. On June 8th, 2025, Mozilla announced that Orbit would shut down on June 26th, 2025, and the extension would no longer be usable.
Pocket was a website for storing and sharing bookmarks. Pocket partnered with Mozilla in 2015 to integrate Pocket into Firefox. Pocket was later acquired by Mozilla in 2017, with plans to open-source its server-side code, although this was never completed. Pocket is scheduled for shutdown on July 8th 2025, with Mozilla stating that this would allow them to focus on new Firefox features.
Fakespot was a website that analyzed reviews on shopping websites, such as Amazon and Walmart, to identify fake or unreliable reviews and provide shoppers with a more accurate representation of products. Mozilla acquired it in 2023 and integrated Fakespot into Firefox Suggest and Review Checker. Fakespot is scheduled for shutdown on July 1st, 2025, with Mozilla stating that Fakespot’s model was unsustainable.
Mozilla Community Pastebin was a dpaste instance hosted by Mozilla. Users could create snippets of text, Markdown, reStructuredText, or code, and share them via link. Its shutdown was announced in February 2025, due to low usage, with the shutdown scheduled for March 31st, 2025.
Mozilla Social was a Mastodon server run by Mozilla. It was announced at the end of 2022, entered private beta in May 2023, and its shutdown was announced in September 2024. No reason was given for the shutdown, and the server is scheduled to go offline on December 17th, 2024.
Firefox Lockwise was a password manager that was built into Firefox on the desktop, and available as an app for iOS and Android. After password management functionality was implemented into the Firefox mobile apps, Mozilla discontinued the standalone Lockwise mobile apps in late 2021.
In 2019, Mozilla announced that it was shutting down its irc.mozilla.org IRC network and looking for alternatives, due to ongoing issues with abuse and harassment, as well as technical barriers. Later that year, Matrix was chosen as the replacement. The IRC network was shut down on March 2nd, 2020.
Firefox Send was an end-to-end encrypted file sharing service. It was suspended in July 2020 due to abuse, and fully shut down in September 2020.
Firefox Notes allowed users to write and sync encrypted notes using a Firefox extension or an Android app. It will be decomissioned in November 2020, and notes will be available only for export.
X-Ray Goggles was a browser extension that allowed users to easily view and edit the source code of any webpage, then share their modifications with others. It was decomissioned in December 2019.
Thimble was an educational, web-based code editor that allowed users to easily create and publish websites. Thimble was shut down by December 2019, and users were given the chance to migrate their projects to Glitch, a similar tool for building web apps.
Lightbeam was a Firefox extension, originally named Collusion, that recorded tracking cookies saved to the users’ browser as they visited websites. It then visualized these cookies in a graph, showing when a cookie was used to track the user across websites. It was discontinued in 2019 in favour of Firefox’s Enhanced Tracking Protection, which unfortunately doesn’t provide the same level of visualization.
SpiderNode was a port of Node.js to SpiderMonkey, Firefox’s Javascript engine, as opposed to Chrome’s V8 engine. It was intended to be used by Positron, a Gecko-based desktop app runtime.
Positron was a runtime for creating desktop apps with web technologies. It was based on Gecko, Firefox’s rendering engine, and SpiderMonkey, Firefox’s Javascript engine (using another project called SpiderNode). Positron aimed to be compatible with Electron, which is built on Chromium and V8.
Mozilla Persona was a cross-browser, decentralized, single sign-in web authentication system. The project was shut down in 2016 due to low adoption.
Firefox OS was an open-source operating system for smartphones, tablets, and smart TVs, based on Gecko (Firefox’s rendering engine), and the Linux Kernel. The sale of Firefox OS smartphones ended in 2015, and development was discontinued in 2016.
Shumway was an HTML5 and Javascript based SWF media player. It rendered Flash content by using an ActionScript interpreter written in Javascript. Declining usage of Flash on the web was likely to have contributed to the discontinuation of this project.
Firefox Hello was a video chat service built into Firefox versions 34 - 49. It allowed users to initiate video calls with one another by simply sharing a link, no account required. While Firefox Hello had good integration with Firefox, it could be used from any browser that supported WebRTC.
Firefox Tilt, which started as a browser extension, and later was added to the built-in developer tools, let you view web pages in 3D. Nested HTML elements would pop out of the page, and you could pan, rotate, and zoom to look around. A demo can be seen in this developer tools update video.
Appmaker was a tool to build mobile apps without code. Instead, it used visual blocks and signals. Appmaker, along with Popcorn Maker, was shut down in September 2015 to focus on Webmaker.
XULRunner allowed developers to create standalone desktop apps based on Gecko, using Mozilla’s XUL (XML User Interface Language). Both Firefox and Thunderbird were built on XULRunner, as well as several non-Mozilla products including Flickr Uploadr, Google Adwords Editor, IBM Lotus Notes, and more.
Camino was a web browser that was built for and integrated heavily with Mac OS X, based on Firefox’s Gecko engine. Camino had a native interface, as opposed to the XUL UI framework used by Firefox. The end of development was announced in 2013.
Ubiquity was an experiment to add a natural-language-based command line to Firefox that helped users get tasks on the web done faster. Ubiquity commands were small pieces of code that any website could provide, which users could choose to subscribe to when available.
Venkman was a Javascript debugger for Firefox. Development had slowed down by 2011, and it was soon superseded by Firebug. A walkthrough of Venkman shows off many of its features.
Deuxdrop was a distributed, secure messaging system, intended for one-to-one and group messaging. Deuxdrop was a continuation of Raindrop, a previous project with similar goals.
Mozilla Prism allowed users to run web apps directly on their desktop, outside of their web browser. It used Firefox under the hood, and added additional capabilities such as offline data storage and hardware accelerated graphics. Prism was available as both a standalone application and as a Firefox extension.
Mozilla Sunbird was a standalone, cross-platform calendar application. Development was discontinued in 2010 to focus on development of Lightning, which shared the same codebase, but was built into Mozilla Thunderbird.
Minimo was a version of Mozilla optimized for small devices, including cellphones and PDAs, that had limited resources. It was available for platforms including Windows Mobile, Windows CE, and GPE. It was later superseded by Firefox Mobile (code-named Fennec).
Mariner aimed to improve the performance and stability of Netscape Communicator. It was open-sourced in March of 1998, but was abandoned in October that year, as Netscape decided to work on its newer NGLayout (now known as Gecko) engine.
ElectricalFire was an open-source, just-in-time Java virtual machine. It was open-sourced by Netscape in 1999 after it was no longer being developed as a commercial product.
Grendel was a mail and news client written in Java, and built on Sun’s JavaMail API. It was an open-sourced portion of the code from Netscape Navigator’s Java rewrite, code-named Xena.
MXR was Mozilla’s fork of LXR, a source code indexer that aimed to improve code comprehension. Eventually Mozilla began working on a replacement tool with better static analysis and UI. This replacement is called DXR, and once it reached maturity, Mozilla shut down their MXR instance.