Mac Safari message says web page using significant energy/memory

A quick search found a lot of people are seeing this, and a few suggestions that it’s not worth worrying about on a Mac that’s not using a battery. But my wife thinks it coincides with her Facebook games lagging and pixelating, and now she’s seeing it with her Yahoo mail and a few other websites.

And Safari’s about the only app she runs on this 8GB 27" iMac that’s just 18 months old. I use a 2013 iMac running Safari, Lightroom, Photoshop, Ulysses, Omnifocus, Omnioutliner, BusyCal, Keyboard Maestro, Alfred, etc, and I’ve NEVER seen a message like this. But then I don’t use Facebook often, and don’t run Flash…

Ideas? She thinks it must be something I did to her Mac and I should be able to fix it.


I see this everyday on my 8GB Mac mini. (The mini is primarily a home server but these days I’m using it for other things more than usual.). If I’ve been reading and clipping articles with Safari, and leave any tabs open, when I return I will normally find at least one tab with this message.

My theory is this can be caused by excessive advertising activity, etc. on these pages.

It’s either crappy web sites, sites with lots of (or badly-written) advertising, or applications that run in a browser. I’ve never had it cause lagging, but sometimes things become temporarily unresponsive in the browser, which might be interpreted as lagging.

It’s nothing you did. It’s simply Safari and macOS notifying her of something that previously they didn’t notify about. I suspect it’s aimed at getting people to understand that the bad online experience they’re having is due to a buried tab somewhere that’s eating up all of the available resources.

Facebook, Yahoo, games in browsers — they’re all likely culprits for this.

One possible fix is to buy and run reputable ad blocking software. This will take care of the warnings that come from ads, but it won’t fix badly-written or resource-heavy applications (lie Facebook games).

I get this on Gmail. I usually just close and reopen the tab and it goes away.

I have an 8GB Ram MacBook Pro 2018 - I used to see this issue a lot more before I had Ad Block Pro installed on Safari…