Are these sites you opened/visited yourself or are these popup/popdown advertisements? You may have something installed in your browser - either sites are pushing some content to you and opening screens behind your browser or you may have some plugin installed which does that. May be popup blocker is needed?
I switched on Popup blocker and installed Add blocker on my daughter's Safari and difference in cpu load, speed and behavior was shockingly obvious. At least go to Security tab in Preferences and check "Block pop-up windows" and see if that helps. And check all Plugins and extensions, which are installed.
Honza1, actually these are not pop-ups. Also I have uBlock Origin installed. I've used Safari with uBlock for ages. This is something new that it seems to be doing.
A good example I ran into yesterday was browsing Amazon. I had Safari open with a few other tabs and opened up Amazon. The entire time, it appears to me, that I am browsing everything in this main Safari window. Yet, after I have been browsing for awhile, I notice processor usage is ramping up, Safari is using tons of RAM, and things were getting noticeably sluggish in the UI overall.
So I click F3, and behind my main Safari window, there's a TON of other open Safari windows of pages that I had been browsing. Except to me, I browsed them in the front-most window, clicked Back button, and continued browsing. Nothing is telling me that these windows are opening in the background.
They are not ads, nor pop-ups. These are pages I have browsed. My suspicion is they are created when I click the Back button, unnoticed in the background, until the computer is slowing down and I now hit F3 to look.
It's very odd. Maybe something else has changed in Safari's handling of tabs/windows that I am unaware of. Something is spawning these zombie windows on me.
[doublepost=1515348293][/doublepost]Actually, I figured it out. It is not Safari, but rather an option that got turned on in the extension called
HoverSee that I must have clicked by mistake. Somehow I must have clicked "
Yes & Add To History" under it's
Advanced > History options tab. Every time I hovered over a photo on Amazon's page, or any other page, to get a better view of the item, it opened these zombie windows in the background, without even realizing. That's why it seemed everything was going along normally in the front-most window.
I was able to replicate it numerous times just now, and the behaviour has stopped with that option turned off.
Thanks to everyone who read this and scratched their heads right along with me.
