Firefox Running Multiple Processes? Here's What's Actually Happening

Tech & Gaming
1

Opened Task Manager recently and saw like eight Firefox processes running at once. My first reaction was “something is wrong” but after looking into it I realized this is actually intentional behavior and worth understanding.

Why Firefox runs multiple processes

Firefox uses a multi-process architecture called Electrolysis (or e10s), which has been the default for several years. The model is similar to how Chrome handles processes:

  • One main process handles the browser UI
  • Separate content processes handle web page rendering
  • Additional processes handle GPU acceleration, plugins, and extensions

The reason for this design is isolation and stability. If a webpage crashes or a script freezes, it should only kill that tab’s process – not the entire browser. Before multi-process, one bad tab could take down everything.

How many processes is normal?

Firefox uses a “web content process limit” to cap how many content processes run simultaneously. The default is 8 on most systems (scaled to available RAM). You can see your current setting at about:config by searching for dom.ipc.processCount.

If you have 12 tabs open and 8 processes, Firefox is reusing processes for some tabs – expected behavior.

Can you reduce the number of processes?

Yes. In about:config, you can set dom.ipc.processCount to a lower number, like 4 or even 2. This will reduce memory overhead at the cost of some stability and isolation. If a shared process crashes, more tabs go down with it.

On a low-RAM system (4 GB or less), reducing this can meaningfully improve performance. On anything with 8+ GB, the tradeoff usually isn’t worth it.

Extension processes

Some browser extensions run in their own processes. If you have a lot of extensions, these show up separately in Task Manager. You can see which extensions are running at about:processes (a newer about: page that’s really useful).

Disabling multi-process entirely

You technically can force single-process mode but Mozilla has removed the UI for this in recent versions. It’s not recommended and the about:config flags for it may not work reliably in modern Firefox.

The short answer for most people: multiple Firefox processes are normal, expected, and largely a good thing. If memory usage is the concern, the content process count setting is the right lever.

2

ngl I had no idea this was intentional. I’ve been closing and reopening Firefox trying to fix this for months. the about:processes page is actually really useful – shows you exactly what each process is and how much memory it’s using. way better than task manager for browser-specific stuff.

3

The process isolation model is genuinely good architecture. Pre-Electrolysis, a single bad ad script could hang the whole browser. Modern browsers all do this now for good reason. The tradeoff is RAM, which is real, but on modern hardware it’s a reasonable cost for the stability you get.

4

The dom.ipc.processCount setting is something I adjust on older machines I occasionally work on. Dropping it to 4 on a machine with 4 GB of RAM makes a noticeable difference in how Firefox feels day-to-day. Worth knowing if you’re supporting older hardware.

5

about:config in general is the underused power user feature of Firefox. There’s a huge amount of behavior you can tune there that has no UI equivalent. The multi-process settings are just one example. Good thread.

6

Worth mentioning that about:processes also shows container processes if you’re using Firefox Multi-Account Containers. Each container context can run in its own process, which adds to the count. Useful for privacy but adds memory overhead.