That gives us the opportunity to discover and squash bugs as we evaluate the right number of process to ultimately enable. (blog.mozilla.org)
Mozilla calls this a «just right» number of processes for many Firefox users, and says it makes Firefox use 30 % less memory than Chrome. (howtogeek.com)
And, if you don't like this, you can head to Firefox's options page and customize the exact number of processes Firefox will use — even setting it to one content process. (howtogeek.com)