See bug comment 5. We should profile this case and see if there is any low-hanging fruit to making the "Forget" snappier in this scenario. Since we're just closing the whole window, I didn't think the number of tabs should have much of an impact, but maybe we're doing something dumb.

> … comment 5. … Which bug, please? Maybe of interest: 874218 - Delay in tab size updates when closing multiple tabs when there are many open <https://bugzilla.mozilla.org/show_bug.cgi?id=874218> – UNCONFIRMED More generally, and recent: Quantum/Flow - MozillaWiki <https://wiki.mozilla.org/Quantum/Flow> ---- As a side note to <https://github.com/kesselborn/conex/issues/48#issuecomment-335016004> I can say, here, that Firefox 56.0 (64-bit) on Tier-3 FreeBSD-CURRENT was reasonably responsive whenever I closed a window that had more than two hundred tabs, with a significant proportion loading or loaded at the time of closure.