The main process is sometimes called the UI process, the chrome process, the browser process or the parent process.

Keep in mind that your process will have to have some mechanism for communication with other processes to be useful, so it is always a potential target.

вЂњI wonвЂ™t run JavascriptвЂќ is not sufficient. This can be legitimate, for example you may need access to some device API that is unavailable to a content process, but the security for your new process will then have to come from a different source. You may, for instance, want to create a new process to escape the confines of the sandbox in a content process. Anything that compromises security is a non-starter. And you will need to consider limitations of some platforms (think Android) where you may not want to or not be able to spawn the new process.Д¬onsult the sandboxing team (#hardening) to discuss what the sandbox for your new process will look like. You will also need a way to efficiently communicate directly with your new process. If you make the decision to do this from, say, a content process, you will need a safe, performant and stable way to request this of the main process. But it means that the main process will need to know to create your process. There is good reason for this, mostly based on our sandboxing restrictions that forbid non-main processes from launching new processes themselves. Currently, all processes in Firefox are spawned by the main process (excepting the launcher process). For example, an applicationвЂ™s process hierarchy forms a tree where one process spawns another. This falls under the category of вЂњFirst, do no harmвЂќ:Д¬onsult the Platform and IPC teams (#ipc) to develop the plan for the way your process will integrate with the systems in which it will exist, as well as how it will be handled on any platforms where it will not exist. Informed by this history, there is some of non-obvious preparation that you should do before starting down this path. The same logic inspired the NPAPI (Flash) plugin process. One of the benefits of the GPU process was that it improved browser stability by separating a system component that had frequent stability issues вЂ“ GPU drivers. For example, we heavily sandbox content processes to protect from external code, while the File process, which is a content process that can access file:// URLs, has a sandbox that is similar but allows access to local files. Sandboxing processes offers great security guarantees but requires making tradeoffs between power and protection. The separation of memory spaces undermines many types of exploits. Site isolation requires additional processes to separate HTML and JS for different sites. Separating HTML and JS from the browser makes it possible to secure the browser and the rest of the system from them, even when those APIs are compromised.Д«rowser stability was also improved by separating HTML and JS from the browser, since catastrophic failures related to a tab could be limited to the tab instead of crashing the browser. Here is an incomplete list of good reasons weвЂ™ve created new processes: Then, implementations on some platforms developed processes for graphics (вЂњGPUвЂќ processes). Then, it split again so that the browser could also disentangle itself from web content (content processes).

Then, one became two as NPAPI plugins like Flash were pushed into their own process (plugin processes) for security and stability reasons. IPDL: Inter-Thread and Inter-Process Message PassingДЇirefox started out as a one process application.

Getting Set Up To Work On The Firefox Codebase.

Firefox gecko driver documentation