Mozilla Firefox is one of the favourite browser as Internet Explorer browsing quality doesn’t meet the expectation. According data from Mozilla, there is around 244 million users around late 2017 and the recent usage is only around 198 million as reported in Q2 2021. This means that Firefox has been losing around 4.6 million users in around 3 years.
At this moment, the most popular browser such as MS Edge, Chrome and Chromium (open sourced Chromium) is based on the Chromium engine while Mozilla retain its stance with the Gecko browser engine. Chromium engine is so popular till that Microsoft ditched their own original MS Edge with Webkit and switch to Chromium instead.
Chromium has always been a favourite browser engine for developers and most common user. At today, there are some web services that can only be run on top with Chromium engine unlike browsers such as Mozilla Firefox and Apple Safari.
While Chromium is common due to the popularity of Google Chrome, Mozilla Firefox offers some advantage in terms of advanced customization with services provided by a privacy centric company. It is still one of the best web browser if you focus on privacy and security. The Onion Router still uses a modified version of Firefox for its anonymous network access.