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Browser.sessionstore.max concurrent tabs

From MozillaZine Knowledge Base

This article has been written for the SeaMonkey tabbrowser. However, most of it probably applies to Firefox too.

Contents

Background

  • Depending on the speed of your browser and of your connection, it may be advantageous to load more or fewer tabs at the same time. This preference allows you to tweak that concurrency (currently when "restarting" but not when "loading the (multitab) homepage", at least in SeaMonkey).
  • This preference also gives access to the "load-on-demand" feature of SeaMonkey and Firefox.

Possible values and their effects

Any negative integer

Restore all tabs at the same time.

0

(Load-on-demand feature) Load only the current tab. For all tabs which haven't yet been current during this session, load only the URL and favicon, but not the page contents.

Any positive integer

Load that number of tabs at the same time. (If another tab is made current, load it too.)

UI

SeaMonkey

Edit → Preferences → Browser → When restoring sessions and windows →

( ) Restore all tabs immediately
(•) Restore [   3] tabs at a time
( ) Only restore tabs when I need them

Firefox

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Caveats and Recommended settings

  • Setting this preference to a negative value may cause your session to start really slowly, unless it includes only a very few tabs.
  • The default value of 3 is probably too low for most modern systems. You may want to experiment with slightly higher values, depending on your CPU speed.
  • If you have extremely many tabs (my home session has more than 700 at the moment — Tony 15:08, 28 January 2016 (UTC)) you may want to set this pref on zero to load tabs only on demand and spare memory.
  • If you restart too soon, while tabs are still loading (especially with this preference set to a negative value) some tabs may appear in the all-tabs menu as "Untitled" even though making them current shows the correct URL in the Location bar. Reload such tabs (e.g. by Ctrl+R) if you don't want to lose their URL at next session restart.

Tips

If you have a fully loaded session with very many tabs, setting this preference to zero in about:config or to "Only when I need them" in the Preferences dialog, then restarting (not closing down then starting up: for instance, in SeaMonkey, clicking "Help → Restart with Add-ons Disabled" then unchecking the checkbox "Restart with Add-ons Disabled" in the ensuing popup) will reclaim most of the memory used by the loaded tabs.

First checked in

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Has an effect in

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Related bugs

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