Firefox 54: multi-process gets another content process

The most recent Nightly version of the Firefox browser, Firefox Nightly 54, ships with two content processes instead of just one.

Firefox's multi-process architecture still rolls out to Firefox stable versions. That process will still take a couple of release cycles to reach all users of the stable version of the Firefox web browser.

Firefox uses a content process for all tabs open in the browser, and a separate process for the browser core.  Separating the core browser from the rest improves stability, and also responsiveness and other metrics of the browser.

If a tab crashes, there is less chance that it will take the whole browser with it doing so.

Mozilla's implementation is different from how Google handles the multi-process architecture in Chrome. Chrome runs any open tab in its own content-process. The upside of this is that it improves stability and also security further. There is a downside to this however as well, as doing so requires more RAM.

Tip: Chrome users can save a bit of memory by configuring Chrome to use one process per site, opposed to one process per tab.

Back in 2016 I explained how Firefox Nightly users can increase the number of content processes that Firefox uses for its multi-process architecture. I enabled eight content processes on the machine back then and have not changed the value since.

I noticed a couple of issues, but nothing too major.

Mozilla has done the same now for the new Firefox 54 Nightly version. It pushed the content processes to two. This marks an important step in the whole multi-process architecture system of the browser.

Two content processes is the next big step, as it paves the way for enabling more than two content processes in the future. The number of content processes that Firefox will eventually ship with by default has not been decided on yet.

While that is done for testing primarily right now, it does mean that Mozilla thinks the implementation is stable enough as it enabled it for all Nightly users who upgrade or install Firefox 54.

The new multi-process setting will trickle down to Firefox Stable eventually, but a schedule for that has not been posted yet.

Mozilla will probably never mimic Chrome's one process per tab behavior. It would increase memory use by a lot. This is not a problem on modern systems with 8, 16 or even more Gigabytes of RAM, but the largest part of Firefox's user base uses machines with 4 Gigabytes of RAM or less.

Last metrics show more than 18% with 2 Gigabyte, more than 15% with 3 Gigabyte, and more than 5% with 1 Gigabyte of RAM.