This addon suspends background tabs to save the memory.
There are some existing addons for this purpose. However, this is defferent from others on the point: this addon unloads only the current contents and fastload caches for "Back"/"Forward", so it don't break metadata related to tabs and provides ability to suspend/restore tabs with less side effects. (On the other hand, because this addon calls very unstable/internal APIs of Firefox itself, this can be disabled by Firefox's update in the future.)
Other similar addons overwrites tab state or close the original tab after duplication, so they can break other tab related addons like Tree Style Tab ( http://piro.sakura.ne.jp/xul/_treestyletab.html.en
). This is started to be developed to solve such compatibility issues.
Similar or Related Extensions
"I cannot trust such an addon which calls internal APIs. Is there any other alternatives which is based on stable/public APIs?"
=> Dormancy ( https://addons.mozilla.org/firefox/addon/dormancy/
) and UnloadTab ( https://addons.mozilla.org/firefox/addon/unloadtab/
) suspend tabs via public APIs, so they are often stabler than this addon.
"I hope to save my CPU resources instead of the memory."
=> Suspend background tabs ( https://addons.mozilla.org/firefox/addon/suspend-background-tabs/
) doesn't unload tabs but stops scripts in background pages.