Something is Preventing My Mac from Sleeping

This is another one of those aha moments using Mac that’s perty nifty. I came in this morning to find my Mac was not sleeping. The screen had been on since I left it last night.

A little bit of Google Fu later, and I learned that Activity Monitor actually has a column just for figuring this out! Too cool!

That last column there is the one. Of course, this bit of advice only applies if you actually have your computer display set to sleep in System Preferences > Energy Saver.

It should be on by default, but I admit that I’ve turned it off a couple times and forgot. So it never hurts to double check in this case.

If you want to “debug” the problem, you can set that “Turn display off after:” slider to lower, like a minute. Pop open Activity Monitor and sort by Preventing Sleep so that the “Yes” values are at the top. Then sit and wait to see what hangs on. the “hidd” process is a system process that responds to user input — so don’t touch the mouse or keyboard or any other inputs while waiting. (Also make sure nothing is sitting on one of your inputs, like your cat, for instance.)

That should narrow down which of the processes is the problem. Then you can try killing them (or quitting) one by one to confirm. You gotta wait again for it to sleep after each one. The reason is that some apps may have their own timer (e.g., Slack) that will let the computer sleep only after their timer has elapsed, which is usually okay. This approach lets you test that timer to see if it is working or not. Otherwise, you can just close the ones with a Yes to solve your problem right away. :)