In the last three years, Firefox has lost about 46 million users. This information has come up in Mozilla's own public data report.
The situation with Firefox was different a few years ago. The once-popular browser has clashed with Apple's Safari and Google's Chrome browser.
In 2018, the number of active monthly users of the browser was about 244 million. The browser lost about 50 million active users in the following years.
As of the second quarter of this year, Firefox currently has 198 million monthly active users.