|Initial release||December 7, 2015|
|Type||Mobile browser, Ad-Blocker|
Firefox Focus is a free and open-source privacy-focused browser from Mozilla, available for Android and iOS smartphones and tablets. Firefox Focus was initially a tracker-blocking application for mobile iOS devices, released in December 2015. It was developed into a minimalistic web browser shortly afterwards. However, it can still work solely as a tracking-blocker in the background of the Safari browser on Apple devices.
In June 2017, the first release for Android went public and was downloaded over one million times in the first month. As of January 2017, it is available in 27 languages. Since July 2018, Firefox Focus is preinstalled on the BlackBerry Key2 as part of the application Locker.
To bypass content-blocker restrictions from Apple, Firefox Focus is using the UIWebView-API on iOS devices. On Android, it has been using the Blink engine in version 6.x or earlier, and GeckoView since version 7.0.
Firefox Focus is designed to block online trackers, including third-party advertising, with the end goal of both improving browsing speed and protecting user's privacy. Content blocking is achieved using the Disconnect block lists. The blocking of third-party trackers (except "other content trackers") is enabled by default. In the other Firefox browsers, users have to enable the Tracking Protection feature inside the browser preferences manually. Users can also view types of trackers on a page by tapping on the shield icon next to the URL bar. A panel will pop-up and shows what kind of trackers are on that page: ad trackers, analytics trackers, social trackers or content trackers.
On December 20, 2018, Mozilla announced that Firefox Focus now checks all URLs against Google's Safe Browsing service to help prevent people from accessing fraudulent sites.
Firefox Focus can be set as content-blocker in the Safari web browser options. After activating the Safari integration in the Firefox Focus settings, it will disable trackers automatically in the background when browsing using the Safari browser.
Pressing the trash icon while browsing will delete all session data and refer to the startscreen, that is displaying the customisable search bar. Tabs can be opened by long-pressing an URL on a website. Favourite links can be set on the homescreen of the device.
Firefox Focus contains a option called telemetry. By activating it, users allow Mozilla to collect and receive non personal-identifiable information to improve Firefox. Due to privacy concerns, telemetry of Firefox Klar is disabled by default.
October 15, 2018, Mozilla announced that Firefox Focus is being updated with a new search feature and visual design. That means the browser will conceptually tell users about its features and options. 
Minimum device requirements
There are some minimum hardware requirements to remove tracking contents. The mechanism needs hardware that can handle the extra load of content blocking so it only works on 64-Bit devices running iOS 9 and above including:
- iPhone 5s and newer
- iPad Air and newer
- iPad mini 2 and newer
- iPod touch from the 6th generation
"Firefox Klar" is the modified version with telemetry disabled released for German-speaking countries in order to avoid the ambiguity with the German news magazine FOCUS. F-Droid uses this flavor due to telemetry being disabled by default in Klar.
- Firefox, the desktop web browser
- Firefox for Android, a project for Android smartphones and tablet computers
- Firefox for iOS, a project for iOS smartphones and tablets
- Safari, the default web browser for iOS
- Mobile browser
- "Focus by Firefox - Content Blocking tor the Open Web - Mozilla". Mozilla Foundation. Retrieved 18 July 2018.
- Mozilla. "Firefox Focus Browser". Retrieved 27 July 2017.
- Ellis, Cat (June 20, 2017). "Firefox Focus private browser arrives on Android". TechRadar. Archived from the original on August 6, 2017. Retrieved 18 July 2018.
- Fingas, Jon (November 17, 2016). "Firefox Focus brings easy private browsing to your iPhone". Engadget. Archived from the original on February 18, 2019. Retrieved 2018-07-18.
- Hern, Alex (November 18, 2016). "Firefox Focus: new app offers very private browsing". The Guardian. Retrieved 2018-07-18.
- Vilches, Jose (November 18, 2016). "Firefox Focus for iOS makes private browsing quick and easy". TechSpot. Archived from the original on July 18, 2018. Retrieved 27 July 2017.
- Nguyen, Nick (November 17, 2016). "Introducing Firefox Focus – A Free, Fast Private Browser for iPhone". Mozilla Foundation. Retrieved 18 July 2018.
- Berger, Daniel (July 21, 2017). "Firefox Klar Eine Million Downloads". heise online (in German). Archived from the original on June 23, 2018. Retrieved 2018-07-18.
- Nguyen, Nick (January 25, 2017). "Firefox Focus Now Available in 27 Languages". Retrieved 2018-07-18.
- "New Features in Firefox Focus for iOS, Android – now also on the BlackBerry Key2". Mozilla Foundation. July 12, 2018. Archived from the original on August 22, 2018. Retrieved 2018-07-18.
- Carrasqueira, João (July 12, 2018). "Firefox Focus gets new Features on Android and iOS and comes to the latest Blackberry". Neowin. Archived from the original on January 7, 2019. Retrieved 2018-07-18.
- "UiWebview". Retrieved 2018-07-18.
- Braun, Herbert (August 12, 2015). "Mozilla veröffentlicht Content-Blocker für iOS". heise online (in German). Archived from the original on July 18, 2018. Retrieved 2018-07-18.
- "What's new in Firefox Focus for Android (version 7) | Firefox Focus Help". support.mozilla.org. Retrieved 2018-09-14.
- focus-android: Firefox Focus: The privacy browser - Browse like no one’s watching, Mozilla Mobile, 2017-11-13, retrieved 2017-11-13
- Brewster, Thomas (November 17, 2016). "The iPhone Just Got A New Super-Private Firefox Browser". Forbes. Retrieved 2018-07-18.
- "Tracking Protection | Firefox Help". support.mozilla.org. Retrieved 2017-11-13.
- Travers, Andrew (February 15, 2018). "Browse, erase, repeat". trvrs.co. Archived from the original on July 19, 2018. Retrieved 2018-07-19.
- Lardinois, Frederic (December 20, 2018). "Firefox Focus adds support for enhanced tracking protection and Google's Safe Browsing service". TechCrunch. Retrieved January 3, 2019.
- Orgera, Scott (August 17, 2018). "Firefox Focus Browser for iOS". Lifewire. Archived from the original on July 18, 2018. Retrieved 2018-07-18.
- Mozilla Wiki: Telemetry
- Telemetry Readme - Firefox Focus on GitHub "Builds of "Focus for Android" have telemetry enabled by default ("opt-out") while builds of "Klar for Android" have telemetry disabled by default."
- Peters, Jared (October 15, 2018). "Firefox Focus for Android gets a big update with search suggestions and a new design". TalkAndroid. Archived from the original on January 5, 2019. Retrieved January 4, 2019.
- "support.mozilla.org - Firefox Focus requirements". Retrieved 2018-07-20.
- "Firefox Focus: Privacy browser by Mozilla". Retrieved 2018-12-23.
- "Was ist Firefox Klar?" (in German). Mozilla Foundation. Retrieved 27 July 2017.
- "I can't find Firefox Focus in Germany, Austria or Switzerland | Firefox Klar Help". support.mozilla.org. Retrieved 2017-07-31.
- "Mozilla Klar (#235) · Issues · F-Droid / Requests For Packaging". GitLab. Retrieved 2018-09-14.
- "Antifeature:Tracking - F-Droid". f-droid.org. Retrieved 2018-09-14.