Mozilla, the company that owns the Firefox browser, has released the list of its most popular extensions of 2021. Surprisingly, the two most popular Firefox extensions of 2021 are ad blockers.

While Firefox users downloaded extensions over 100 million times, two ad blockers stood out from the crowd, with more average daily users than any other extension type.

Mozilla has announced the most popular add-ons in Firefox. In a blog post, Mozilla said that about a third of all Firefox users have an add-on installed, including themes and extensions.

According to numbers shared by the company, there were around 127 million add-on installs. Extensions were the most popular, with over 109 million installs. That's to be expected since extensions add extra functionality to the browser.

Somewhat surprisingly, the two most popular extensions for 2021 were both ad blockers. Adblock Plus took the mantle as the most popular extension with an average of slightly over six million daily users, followed by uBlock Origin, which had an average daily user count of five million.

Another exciting observation is that 60 percent of Russian Firefox users have installed an add-on.

From Firefox's top extensions, an online privacy theme is constant. Other honorable mentions include Firefox's Facebook Container extension and Ghostery, both of which boast over one million daily active users on average.

Related: Reasons to Switch From Google Chrome to Mozilla Firefox

Adblock Plus Firefox extension

Ad blockers topping Firefox's list of popular extensions is quite interesting and fits into the central theme of users being tired of intrusive advertising. Intrusive ads being those annoying ads that impend your browsing experience.

Adverts in themselves are not bad. For one, they help businesses get their word out there, and, secondly, they help your favorite websites and content creators keep their content free and accessible to all.

The reason why ad blockers have topped the charts on Firefox could also be due to the rising concerns over digital privacy. Privacy has been a big concern in 2021, especially after the Meta-owned WhatsApp announced its controversial privacy policy change.

Related: How to Use Add-Ons in Firefox for Android

Step Up Firefox Browser's Functionality With Extensions

Extensions are popular due to their inherent nature of adding more functionality that might otherwise not be offered natively in your browser. There are tons of Firefox extensions out there, and it can be hard to filter the wheat from the chaff.

For instance, if you're interested in privacy extensions, there are several available that you can install in one click.