Mozilla added support for multiple content processes in Firefox 54 Stable. The company tested the functionality in development versions of the Firefox web browser before and made the decision to enable content processes in Firefox Stable based on test results in those development versions.

Current stable versions of the Firefox web browser make use of four content processes which means that multiple sites share a content process when multiple sites get opened in the browser.

This means that websites will share a process for data; this is different to how browsers that are based on Chromium handle this as they launch a new process for every page open in the browser and also for plugins.

Why would you change the number of processes?

Firefox users who operate low-RAM systems, e.g. a PC with 2 Gigabytes of RAM, may consider reducing the number of content processes to make Firefox use less RAM.

Users who operate systems with plenty of RAM may consider increasing the number of processes to improve stability and security further.

Changing Firefox's multi-process content processes

Firefox would not be Firefox if there would not be an option to play around with different content process values.

Firefox used one content process initially when the feature first launched but that was bumped to four content processes quickly after successful tests.

Nothing is keeping users from increasing that limit to use more than one content process.

Each content process is listed as firefox.exe on Windows with no distinguishing information-

Firefox runs as many content processes as you see listed there, provided that multi-process use is enabled in the browser.

dom.ipc.processCount

It is rather easy to change the number of content processes. Here is how it is done:

Type about:config in Firefox's address bar and hit enter. Confirm you will be careful if a warning appears. Search for the preference dom.ipc.processCount. Double-click on it and change its value. The default value is 1, indicating that one content process is used. Restart Firefox afterwards. Easiest way to do that is Shift-F2, type restart, hit enter.

Firefox will use the selected number of content process after the restart.

Please note that it will use more memory when you increase the number of content processes in multi-process Firefox, and less memory if you reduce the number.

Mozilla ran some memory benchmarks recently and found out that multi-process Firefox will use between 10% to 20% more memory initially with one content process enabled, and about double the memory with 8 content processes.

This is probably one of the main reasons why Mozilla launched the multi-process architecture with one content process initially and increased it to (just) four in recent stable versions of the web browser.

Ideally, from a stability and security point of view, you'd separate each tab, plugin and the browser UI individually.

Summary Article Name Change how many processes multi-process Firefox uses Description Find out how to change the number of processes Firefox uses when its multi-process architecture Electrolysis is enabled. Author Martin Brinkmann Publisher Ghacks Technology News Logo

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