Too Many Firefox Processes

[MPSmithSTC]

I have one Firefox window open, with two tabs, yet I have 48 Firefox processes running, using between 12 MB and 350 MB of RAM each, with all instances of Firefox using a total of about 1.5 GB of RAM.

WTF!?

[siffemcon]

All browsers run multi-process now. 1.5 GB of RAM is actually quite little, so don't worry about it.

https://support.mozilla.org/en-US/questions/1396420