Why does the browser load the disk at 100%?

Question

Windows

This was not the case before. Removed 90% of add-ons, cleaned with "CCleaner", defragmentation is not required, checked for viruses.

Answer 1

You need to make sure that performance suffers from Firefox. You can still bookmark

Performance

.
If so (work with the disk or CPU), then open a new tab and type in the address bar about:performance. It will show which bookmarks have the most significant impact on performance.
Sometimes it is useful to disable (deactivate) all add-ons and try to visit the same sites.
Ads can be automatically cut using DuckDuckGo Privacy Essentials and this can improve performance.

Answer 2

And who said that it loads the browser? Don't you see that the hard is 100% full, and the hard is occupied by the browser at the most by 1%
That is, 99% of the hard is obviously not consumed by the browser. Usually they eat it like this in Windows ... any system processes or Windows updates are simply not displayed in this list by default ...
It is necessary to open the performance tab in the manager and at the very bottom press the link to open the resource monitor and already there specifically look at what kind of process eating hard. But as I said, most often these are Windows updates.