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Mozilla today launched Firefox 63 for Windows, Mac, Linux, and Android. The release brings Enhanced Tracking Protection, performance improvements on Windows and macOS, search shortcuts, and Picture-In-Picture on Android.

Firefox 63 for the desktop is available for download now on, and all existing users should be able to upgrade to it automatically. As always, the Android version is trickling out slowly on Google Play.

According to Mozilla, Firefox has about 300 million active users. In other words, it’s a major platform that web developers must consider.

Windows, Mac, and Linux

Firefox 63 for desktop brings support for Enhanced Tracking Protection. To explain this feature correctly, we must look at its predecessor.


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Mozilla added Tracking Protection to Firefox 42’s private browsing mode in November 2015. It blocks website elements (ads, analytics trackers, and social share buttons) that can track you while you’re surfing the web. The feature’s blocking list, which is based on the tracking protection rules laid out by the anti-tracking startup Disconnect, is published under the General Public License and available on GitHub.

With the release of Firefox 57 (Firefox Quantum) in November 2017, Mozilla added an option to enable Tracking Protection outside of private browsing. Tracking Protection isn’t on by default because it can cause websites to break, as well as cutting off revenue streams for small websites and content creators who depend on third-party advertising.

In August, Mozilla announced Firefox would block trackers by default in three steps:

  • Blocking trackers that slow down page loads. This feature, aimed at improving page load performance, will be tested in September. If it performs well, Firefox 63 (slated for October 2018) will start blocking slow-loading trackers by default.
  • Removing cross-site tracking that follow users around the web. This feature, which strips cookies and blocks storage access from third-party tracking content, will be tested with some Firefox beta users in September. Mozilla plans to bring this protection to all users in Firefox 65 (slated for January 2019).
  • Mitigating harmful practices such as trackers that fingerprint users (to identify users by their device properties) and cryptomining scripts. Mozilla didn’t share when future versions of Firefox will stop these practices, but it did say they will also be blocked by default.

That schedule has changed with today’s Firefox 63 release.

Firefox 63’s Enhanced Tracking Protection blocks cookies and storage access from third-party trackers, which Mozilla says targets the problem of cross-site tracking without breaking sites and impacting revenue streams like the original Tracking Protection. It does this by preventing known trackers from setting third-party cookies — the primary method of tracking across sites — but still gives you the option to block all known trackers (under Firefox Options/Preferences).

As for blocking trackers that cause long page load times, Mozilla says it is still tweaking the design:

Why? There are a number of reasons: the initial feature design was similar in nature to the original Tracking Protection functionality (including ad blocking) but blocking only occurred after a few seconds of page load. In our testing, there was a high degree of variability as to when various third-party domains would be blocked (even within the same site). This could be confusing for users since they would see blocking happen inconsistently.

A secondary motivation to block trackers and ads on slow page loads was to encourage websites to speed up how quickly content loads. With the tested design, a number of factors such as the network speed played a part in determining whether or not blocking of trackers and ads would occur on a given site. However, because factors like network speed aren’t in the control of the website, it would pose a challenge for many sites, even if they did their best at speeding up content load. We felt this provided the wrong incentive – it may cause sites to prioritize loading ads over content to avoid the ads from being blocked, a worse outcome from a user perspective.

It’s not clear if the next version of Firefox will included these changes, but either way we’ll be hearing more about Mozilla’s approach to blocking trackers in 2019.

Search shortcuts essentially pins sites like Google and Amazon on the new tab page. When you click or tap them, you’re redirected to Firefox’s awesome bar, which automatically fills the corresponding keyword (@google or @amazon in this case) for the search engine. This way, you can type your query, hit enter, and get your search results without having to first load the Google or Amazon homepage.

This feature is a bit of an experiment, and thus limited in scope: It only works for U.S. users. You can remove the default Google and Amazon top sites (click on the dots icon and select “unpin”) and add your own (click on the three dots on the right side of your Top Sites section and select “Add search engine”).

Here’s the full Firefox 63 for desktop changelog:

  • Performance and visual improvements for Windows users: Moved the build infrastructure of Firefox on Windows to the Clang toolchain and Firefox theme now matches the Windows 10 OS Dark and Light modes
  • Performance improvements for macOS users: Improved reactivity, faster tab switching, and WebGL power preferences allow non-performance-critical applications and applets to request the low-power GPU instead of the high-power GPU in multi-GPU systems
  • Added content blocking, a collection of Firefox settings that offer users greater control over technology that can track them around the web. Users can opt to block third-party tracking cookies or block all trackers and create exceptions for trusted sites that don’t work correctly with content blocking enabled
  • WebExtensions now run in their own process on Linux
  • Firefox now warns about having multiple windows and tabs open when quitting from the main menu
  • Firefox now recognizes the operating system accessibility setting for reducing animation
  • Added search shortcuts for Top Sites: If Amazon and Google appear as Top Sites tiles on the Firefox Home (New Tab) page, when selected these tiles will change focus to the address bar to initiate a search
  • In the Library, the Open in Sidebar feature for individual bookmarks was removed
  • The option to Never check for updates was removed from about:preferences (use the DisableAppUpdate enterprise policy as a substitute)
  • The Ctrl+Tab shortcut now displays thumbnail previews of your tabs and cycles through tabs in recently used order (activated only in new profiles and can be changed in preferences)
  • Resolved an issue that prevented the address bar from autofilling bookmarked URLs in certain cases
  • Refreshed visual style of Developer Tools menus to improve navigation and consistency
  • The Dev Tools accessibility inspector is now enabled by default. This tool surfaces information exposed to assistive technologies on the current page, allowing you to check what’s missing or otherwise needs attention
  • Added support for Web Components custom elements and shadow DOM
  • The inspector now ships with a Font Editor that allows you to control non-variable as well as variable fonts

If you’re a web developer, more details are available for you here: Firefox 63 for developers.


The only major new feature for this Firefox for Android release is a picture-in-picture mode (Android Oreo and up). This means that if you’re watching a video in full-screen, when you switch away from Firefox it will move the video into a small floating window, which you can tap to return to the full video player.

Here’s the full Firefox 63 for Android changelog:

  • Added support for Picture-In-Picture video
  • Started using notification channels
  • Locales added: English from Canada (en-CA), and Ligurian (lij)
  • App now targets Oreo with security and performance improvements and support for new features

Mozilla releases new Firefox versions every six to eight weeks, and Firefox 64 is currently slated for mid-December.

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