[frik]

Chrome 1+, IE 9+ and Safari 7+ spawn child processes with less permissions ("sandbox") for almost every tab.

Sadly Firefox 39 (nightly) still has no real multi process support. There are only two processes, the main process holds all tabs, the single child process "plugin-container" holds all plugins (Flash, Acrobat, etc.). It's a bit disappointing to see such little progress since 2010. Hopefully Mozilla's Rust based Servo engine comes to the rescue soon and replaces gecko and its old XUL (XML based UI framework) with Servo and an HTML5 based UI (like Firefox OS).

I use Firefox as development browser because of Firebug and and the new developer tools. Working with dozens of tabs open for days is only possible with IE11 and Chrome.

[dblohm7]

"Sadly Firefox 39 (nightly) still has no real multi process support. There are only two processes, the main process holds all tabs, the single child process 'plugin-container' holds all plugins (Flash, Acrobat, etc.)."

That is incorrect. There is one plugin-container for each plugin module. All Flash instances share a single plugin-container, all Acrobat instances share a single plugin-container, and so forth.

As for the e10s content process, for the moment there is only one content process. The plan is to get e10s working well with the one content process, and then start scaling that up to multiple content processes. Nightly is a bleeding edge development channel, after all.