The most popular extensions and themes for Firefox of 2021

Mozilla Firefox is an application that is not living its best moments, and, what’s more, its golden years are long gone. However, Mozilla’s web browser still has its loyalists, so let’s look at some of the most popular or innovative themes and extensions of 2021.

During the year 2021, 109,508,891 extensions and 17,285,192 themes were installed. These numbers, especially their difference, should not surprise us. Many users tend to leave the aesthetic theme offered by default while trying to personalize the experience, mainly the browsing experience, through the extensions.

Blockers lead the extension ranking.

The extensions dedicated to blocking content displayed on the web have been the most popular, which should not be the least bit surprised at this point. Adblock Plus has averaged 6,134,231 daily users, while uBlock Origin has averaged 5,011,974 throughout 2021.

Although Adblock Plus and uBlock Origin are usually the most popular solutions for blockers, that doesn’t mean they are the only ones that stand out. Facebook Container, which Mozilla itself developed to put barriers to tracking carried out by the ecosystem of services of the “Zuckerberg universe,” has had 1,740,395 daily users. In contrast, the well-known Ghostery has had an average of 1,167. 938.

The Firefox Extensions website has been visited more than 133 million times. Most of these visits come from China, which is followed, in that order, by the United States, Germany, France, and Russia. Mozilla has highlighted that 60% of Russian Firefox users have installed some extension.

Themes, from what we have been able to verify, are not even half as popular as extensions, which is expected if we consider that customization is not something important for many users, so since the foundation, they have been limited to mention the most popular topic: Matte Black (Red). Without further ado, we show what it looks like in Fedora Linux with GNOME and in Windows 10.

Most Innovative Firefox Extensions of 2021

Mozilla has commented that it has been debugging its recommended extensions program for Firefox to list third parties that meet its highest standards of security, usefulness, and user experience. Apart from what has been mentioned so far, the foundation has published a list of innovative extensions through this program.

Tab Stash

Are you one of those people who open tabs indiscriminately and, despite being saturated or overwhelmed, do not want to lose them? Tab Stash allows you to save those open tabs that have not been read or want to be kept in temporary bookmarks, which can be treated as easily navigable links or permanently saved in individual or grouped bookmarks. Also, it is compatible with Firefox Sync.


Stylebot is an extension that allows you to radically alter the appearance of a web page without the need for deep design or programming knowledge. Its features include automatic saving of changes, a “magic editor” to modify and improve readability with a couple of clicks, and provides a CSS code editor for advanced users.


Derived from the Tree Style Tab, the Sidebar is based on the concept of organizing open tabs in a cascading tree format so that they are “hidden” on the side of the browser. The purpose is to facilitate the management of a large number of tabs. Supports management of containers such as Facebook and multi-accounts for the browser, simple bookmarks with drag and drop support, mouse controls with the right button, snapshots, and color customization.

Automatic dark

Mozilla has closed its list with automatic dark, which takes care of modifying the theme or colors used by Firefox based on the time of day. In this way, the application can be adapted to offer better readability depending on the time of day.


As we can see, Firefox still offers exciting things, either through extensions or by introducing new features in the application, such as RLBox and Site Isolation. These two security features have reached version 95 of the browser.

However, and despite the efforts of Mozilla, Firefox has struggled for years not to compete against Chromium (as a technology) and Chrome (as an application), but not to fall into irrelevance. The only strong bastion left to the browser is Linux users, where it remains strong thanks to the conviction of users and that it comes pre-installed in most distributions.

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