For years, multiprocess support has been a thorn in Firefox’s side. Mozilla worked on it for eight years, and after a partial implementation in version 48, the complete system now arrives with Firefox 54. Users have the option to tweak its behavior with a minimal setting, but Mozilla believes they have struck a good balance between performance, security, and memory usage.
Firefox has become multiprocess. Though it arrives a little late compared to its direct competitors, the support is finally here, and we welcome it. According to Mozilla, Firefox 54 is the best version so far, and after using it for a while, I must admit that everything feels a bit faster and more stable. The first advances in multiprocess support were seen in Firefox 48. If the browser installation met the necessary conditions, it would split execution into one instance for the interface and another for content. Why do we talk about “necessary conditions”?
Basically, it comes down to extensions. Mozilla delayed the implementation of multiprocess support because it broke a large number of extensions. With the arrival of the WebExtensions API, the situation improved and developers can move faster, but if the user has an extension in their browser that is not compatible with multiprocess, Firefox will return to its traditional mode. What we see in Firefox 54 is an expansion. The browser now uses one process for the general interface and four for content. Mozilla sees this as “the right balance” and did not hesitate to highlight memory consumption, much lower when compared to Chrome/Chromium numbers. By creating one process per tab, Chrome adds redundant code, and its memory pressure gets out of control.
The most interesting thing is that Firefox users can adjust the number of processes in about:config. If there is plenty of RAM on the computer (or on the contrary, it is very limited), the command is dom.ipc.processCount. Each user will have to explore on their own, and Mozilla is considering adding the parameter to the interface for greater convenience.
