Now in version 84,0 (64-bit) version tabs crash very often. Never before. Just now I had been browsing on several tabs and watching Netflix on another screen. I checked in Task Manager (screenshot attached). Which showed 83% memory usage - but by arranging all running programmes this could not be correct as I have 32Gb RAM. Speccy report attached. I closed Firefox. No change in either Task Manager or Speccy on memory usage. Then I ran System Mechanic Pro which cleared a lot of junk internet files. And then checked Task Manager and Speccy again: 9% memory usage. This sounds about right. My amateur assumption is that this version of Firefox does not clear closed tabs etc from the RAM memory - which leads to it becoming clogged. Pros should know. And be able to solve this nuisance. Thanks for help!