We’re very excited to report that 85% of Firefox 4 users have chosen to install an add-on — that’s more than 60 million users every day! This number doesn’t include Personas, and even excludes popular add-ons bundled with other software that the user hasn’t actively agreed to install.
Firefox 4 desktop add-on usage from March 22 through June 19, 2011, excluding Personas and several commonly-bundled add-ons
When we first saw this number, we expected it to drop as more and more users upgraded to Firefox 4; remarkably, it has stayed between 89% and 85% since launch in March. It’s also interesting to note that on the weekends when Firefox (and Internet) usage slumps, the percentage of users with add-ons increases, indicating those who browse on weekends are more likely to have customized Firefox.