[danohuiginn]

"Generally, MAU [monthly active users] fluctuates over the course of a year, dropping in the summer months and during holidays"

That seems to fit what's happening here. Longer term, firefox seems to have lost 15-20% of users in the past 3 years, which is substantial but not catastrophic. On the other hand, that probably means a much steeper decline in market share.

[cbarrick]

If you change the region from "Worldwide" to "United States", you can see a much more concerning long-term trend.