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Firefox has a setting "Don't load tabs until selected" (see How do I make Firefox 13 Load All My Tabs on Startup or when Resuming Reload). I like that behaviour.

I am searching for a way to "deload"/deactivate a tab manually for a session (until I reload it).

It should stop all running JavaScript functions and plugins (like Flash). The whole webpage content may disappear until I reload/re-activate the tab, but that is not a requirement. The title has to be displayed as tab label (like it is the case with the startup setting, too).

The workaround would be to restart Firefox and don't switch to the tab I want to be deactivated. This is pretty annoying, of course.

EDIT: Here is what I found so far

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You can pin it as an app tab as a work around, but you do realize you're effectively moving the bookmarks bar above the address bar right? – Aug 13 '12 at 23:00
UnloadTab appears to be back. – BrenBarn Jun 29 '14 at 1:29
up vote 7 down vote accepted

In one of the links you referenced at Tab Utilities: Feature Request, there is already an answer from the developer (scroll down to comment no. 4) on how to do this. The answer is to:

  • Add the Restart Tab item to the context menu.

Why it's called "Restart Tab" and not "Unload Tab", I don't understand, but he says you can just change it if you want. Set:

  • to "Unload Tab".

By the way, at the moment it only works on tabs that are not selected/focussed. In other words, if you do "Restart Tab" on the currently open tab, it will just reload. You have to switch to another tab, then right-click on the tab you want to unload, and choose "Restart Tab".

Here are the instructions from the developer, I updated them a little:

  1. Set browser.sessionstore.max_concurrent_tabs to 0 in about:config. (BarTab Lite or Load Tabs Progressively extension should also work.) [ the above is outdated, in current versions of Firefox, go to preferences/options for Tabs, and check "Don't load tabs until selected". ]

  2. Unload tabs manually with Restart Tab or Restart All Tabs menuitem. [ first you have to make sure the "Restart Tab" item is added to the context menu, in Tab Utilities preferences/options -> Appearance -> Menus -> Tab Context Menu ]

  3. Unload tabs automatically after a specified period of inactivity with extensions.tabutils.restartAfter option (minutes).

  4. Tag bookmarks with "norestart" to make an auto-unload black list.

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All Tabs Helper and Auto Unload Tab do this, among other things.

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Auto Unload Tab works well for me and is being maintained it appears. Thanks! – dbasch Apr 4 at 8:13

Tab Utilities has this feature:

11. Auto-restart/unload tabs after a specified period of inactivity

BarTab also can do this:

It also allows you to free memory by unloading already loaded tabs, either manually or automatically.

It did not work for me, specifically because of Flash. Although there are plenty positive feedbacks. Also note, it has been included into FF core recently.

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Thanks bytebuster, I updated my question with these two. Unfortunately, BarTab is no longer maintained, and Tab Utilities seems to miss the functionality to unload a tab manually (instead of automatically), e.g. by right-clicking at the tab and selecting something like "Unload tab". – unor Sep 2 '12 at 2:03

To complete the list there is yet another add-on Suspend background tabs (created by author of AdBlock Plus) that suspends some actions on inactive tabs (such as updating page content with the time). It doesn't affect Flash, videos or downloading on the tabs.

"Currently this extension will only suspend periodical actions happening in background tabs, these will only be resumed when the tab becomes active again. Lengthy downloads in background tabs are unaffected by the current version, as are videos or Flash. So some websites will still manage to make your browser slow despite being in background but that should be far less common now."

"suspend all timeouts for a tab"

"This doesn’t completely disable all activity in the background tabs of course. Network requests will continue, videos will also keep playing."

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This addon has been deadpooled – lkraav Aug 9 '15 at 9:44

There is the extension BarTab Lite X. This is a light extension. Its feature for unloading tab works with recent Firefoxes.

However, better check that unloaded tabs don't mess up Firefox' session restore.

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If you have e10s enabled, taskkill /f /im plugin-container.exe or your OS equivalent is a pretty easy solution.

Firefox will think the content process has crashed, but that is wrong.

Clicking on a tab will reload it.

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