Hidden tabs

[required_alias]

Had to close an app with CTRL-ALT-DEL.
Noticed "Firefox 47." I also noticed, when I add a tab, the number increments by one. Removing a tab decrements by one.
I have one instance of FF open with 7 tabs. where are the other 40?

[morat]

Are you talking about 47 processes or tabs? Try opening the about:processes and about:performance tabs.

There is a list of processes in the Process Manager tab. (about:processes)

There is a list of tabs in the Task Manager tab. (about:performance)

Some tabs have additional subtasks, that may include subframes, trackers or service workers associated with the tab.

It's possible to hide tabs with an addon.

Hide Tabs
http://addons.mozilla.org/firefox/addon/923934

[required_alias]

The reason I started killing apps was my PC is running slow. Once I found the number beside "Firefox" is directly related to my number of tabs, my goal was to kill unneeded ones.
Per Task Manager, FF is using >50% CPU and >50% memory.

[morat]

It's possible for a single tab to have more than one process like a manga site may have the website process and a disqus.com (comment hosting service) process and a accounts.google.com (google adsense) process.

Process Manager and Task Manager - see whether tabs or extensions are slowing down Firefox
http://support.mozilla.org/kb/task-mana ... ng-firefox

Firefox uses too much memory or CPU resources - How to fix
http://support.mozilla.org/kb/firefox-u ... -resources

The best way to speed up Firefox is to use a content blocker.

uBlock Origin
http://addons.mozilla.org/firefox/addon/607454