2 firefox.exe running in the background whenever I open Firefox | Firefox Support Forum | Mozilla Support
This could indicate that your Firefox is using a new "multiprocess" feature.
One of the headline changes in Firefox 48+ is e10s, which separates the browser interface process from the page content process. The performance impact of this can vary a lot between systems: many users find it faster, some find it slower, for many it's neutral. There probably is somewhat more memory use than when everything runs in a single firefox.exe process.
Are you using e10s?
You can check whether you have this feature turned on as follows. Either:
- "3-bar" menu button > "?" button > Troubleshooting Information
- (menu bar) Help > Troubleshooting Information
- type or paste about:support in the address bar and press Enter
In the first table on the page, check the row for "Multiprocess Windows" and see whether the number on the left side of the fraction is greater than zero. If so, you are using e10s.
If you are using e10s:
If you think Firefox is not performing well or is using an unreasonable amount of resources now, you could evaluate whether e10s is causing this problem by turning it off as follows:
(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.
(2) In the search box above the list, type or paste autos and pause while the list is filtered
(3) Double-click the browser.tabs.remote.autostart.2 preference to switch the value from true to false
Note: the exact name of the preference may vary, but it will start with browser.tabs.remote.autostart
At your next Firefox startup, it should run in the traditional way. Any difference?