This is a question we’re asked often and have been trying to answer for some time. We’re very excited to say that we now know that answer: at least a third of Firefox users have an add-on installed!
We first tried to tackle this question last year, but the huge amount of data addons.mozilla.org processes led us to call for the help of the Mozilla Metrics Team. Thanks to the help of Simon Krueger, a metrics intern this summer, we now have some insight into the number of add-on users.
On June 22, addons.mozilla.org received 253.7 million add-on update pings, 244.7M of which were for Firefox add-ons. Firefox sends an update ping for each installed add-on once every day it is running, and at other unscheduled times such as installing an incompatible add-on and Firefox upgrades. Not all update pings go to addons.mozilla.org, however — only add-ons hosted there and add-ons that have not set their own URL to check for updates.
Of all of those pings, we counted 32.8M unique IP addresses. This means that the minimum number of active daily users with at least 1 add-on installed was 33.8M, or 33% of Firefox users.
But what about homes and businesses that have multiple computers behind the same IP address? To estimate a number that takes NAT into account, we looked at the number of blocklist pings Firefox sent on the same day, which is how we measure the number of Firefox active daily users. There were 98.6M blocklist pings that day from 61.5M unique IPs. If we apply that ratio to the add-on pings, our estimate jumps to about 52.6M add-on users that day, or 53% of Firefox users.
For more information on the technical details of this analysis, please read Simon’s post at the Blog of Data.
It’s important to keep in mind that all of the above numbers are active DAILY users. To get the number of monthly Firefox users, we multiply ADU by 3.
A minimum of 33% of users having chosen to install add-ons is great news, and is higher than our previous estimates. It’s especially exciting that we have a new metric to track the success and adoption of add-ons as we launch new features and campaigns encouraging users to customize Firefox and make it their own.