Automatically unload inactive tabs in Firefox

Published: January 12th 2026 (week 3 of 2026)

Even if you are using a completely reasonable amount of tabs, say around a thousand, memory usage of Firefox may grow over time. Tab unloading to the rescue!

How can you turn it on? You have to adjust a few variables in about:config. As always, be careful when changing any values through the about:config interface.

Whether the feature is enabled at all

browser.tabs.unloadOnLowMemory

First, you must enable the feature by setting the unloadOnLowMemory variable to true. Without this, the other changes will be ignored.

"Low" memory threshold

browser.low_commit_space_threshold_percent

Unloading is a memory-saving measure, and is only triggered when the system gets low on available memory. If you want it to be triggered by tab inactivity regardless of available memory, set the low_commit_space_threshold_percent variable to 100.

Inactivity timeout (milliseconds)

browser.tabs.min_inactive_duration_before_unload

Adjust to your own taste. I set it to 3600000 (as suggested by the Arch Linux wiki), and it works well for me.

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