• Mozilla ad blocker Focus is based in part on Disconnect's open source blacklist, and more transparent compared to other ad blockers.

Mozilla ad blocker Focus is based in part on Disconnect's open source blacklist, and more transparent compared to other ad blockers. (Photo : Twitter)

Mozilla unveiled another selection of content blockers called Focus on iOS platform.

The browser maker said Focus is based in part on Disconnect's open source blacklist, and more transparent than many other content blockers, PCMag reported. It allows users to block categories of trackers such as those used for ads, analytics, and social media, and also promises to increase performance on mobile devices by blocking Web fonts. 

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Focus, which changed its name due to a clash with the Signal encrypted communications app from Open Whisper Systems, offers similar blockers to the Tracking Protection feature Mozilla recently released in Firefox 42. It bases decisions to load or block code based on a series of rules and a blacklist of barred content.

The new ad blocker will also identify new trackers on the fly, using heuristics to identify any content following a user from site to site. Focus will only work with Safari because of the way iOS manages content blockers, but Mozilla is hoping Apple will open the system up in the months to come, allowing users to combine Focus with Firefox.

The software represents the latest effort to beat back the uncontrollable increase of intrusive ads and other unwanted Internet software that often bedevils Internet users.

Mozilla's Chief Legal and Business Officer, Denelle Dixon-Thayer, said that content blockers need to be transparent with publishers and other content providers about how lists are created and maintained, instead of placing certain content in a permanent penalty box.

Users can download Focus for free. There are also plans to launch an Android version of Focus, but there is no exact launch date, according to Forbes