(This is really an annoyance in the form of a question.)
Do Macs even really sleep these days? I have an old (Intel) desktop, and I’ll tell it to sleep (using “sleep” in the Apple menu), and the screen goes dark and the fan spins down… but then later I’ll come back in the room and the fan is on, or I can hear the external drive (some old files and Time Machine backups) spinning or spin up/down… it’s not asleep!!!
I know my desktop has been sucked into my iPhone ecosystem (my Apple life?), so it is monitoring phone calls and text messages… but I’d really prefer that sleep make it actually sleep (in my mind, perhaps erroneously, that means "it acts like it’s off but with a fast restart). Maybe there are some settings in Preferences I need to tweak?
Does it wake up on its own even when that disk is not attached? I have a vague recollection of drives not sleeping properly or waking up sleeping Macs. Also, have you set your Mac to wake for network access?
I will say that I also have this suspicion that modern Macs do not actually sleep uninterrupted until you wake them. My M1 Pro MBP routinely will show new email in my inbox when I wake it after ariving at work. I have assumed that somehow it wakes up in my backpack when it sees a known wifi on the way (which it always will thanks to Eduroam and walking across almost a mile of campus on the way to my lab) and then uses that to do background tasks such as check for email. There is the setting “Wake for network access” which I have NEVER turned on on my portable Macs and yet I’m almost certain this MBP still wakes up uncommanded by me at least briefly for some network activity. Back in the Intel MBP days there also used to be a distinction between sleep and hibernation and there used to be sleep files and yada yada, but as far as I’m aware all of that is gone with Apple silicon Macs. I’d still like to have a setting to say basically, never wake up no matter what until I tell you to.
You can test if it wakes to receive mail by setting a rule that applies to any message and makes some trivial change (for example, ‘Change the message color’ or ‘Add a Flag’). If you’re sure all your Macs are asleep, and the rule changes an arriving message, you’ll have your answer. You can then delete the rule and manually undo the change.
In addition to what everybody else has said, it is well-known that some USB devices seem to interfere with Macs going to sleep.
For instance, I’ve an old MacAlly iKey keyboard which, when plugged into a modern Mac, wakes the computer within seconds after it goes to sleep. So if your Mac is configured to sleep when idle, you will find it periodically going to sleep, and then waking up immediately afterward (including spinning hard drives down and up). Annoying and probably not good for the hardware.
I’ve also seen other USB peripherals, including some hard drives, do this.
USB input devices being able to wake a Mac from sleep on connect is a necessary condition for clamshell mode. Now, why a hard disk should also do that or why USB connect also wakes a desktop Mac where clamshell isn’t relevant is certainly up for debate.
Perhaps the explanation is as simple as, connect is easy to detect accurately (keep in mind this has to be implemented on the firmware level), unlike eg. is that just connected device a KB or mouse?
I think there are just some poorly-designed USB interface chips.
Of course an HID device needs to be able to wake the computer, but it shouldn’t do that when it isn’t in use (pressing a key or clicking a mouse button).
The iKey dates back to when Apple had a proprietary power button on the keyboard, and this keyboard has that button. It may be as simple as the keyboard’s chipset drawing excess power in order to make that button work, confusing a modern Mac that doesn’t expect to find that proprietary button.
As for hard drives, I can’t think of a logical reason, but I’ve seen the behavior.
Great comments everyone, thank you! This is what I am here for!
Yeah, power nap is off… it really shouldn’t be doing anything. Often I tell it to sleep and it does but then one of the external hard drives spins back up a few seconds later. Or I’ll come back later and the internal fan is on, so some process(es) is making it work a fair amount (oh I could use the Activity Monitor…). Weird. I love OSX, love that it is Unix / NeXTSTEP (ok ok macOS to keep with the branding), but wow is it complex these days.
My 2018 MacMini normally goes to sleep, in the sense that the screen goes black and I have to enter my password to turn it on. However, it stays awake all the time whenever weather.com is open on the screen in my broswer (Firefox). I have not notices any other web sites that keep the Mini from going to sleep, but I may have missed them.
With the advent of my M1 MacBook Pro, it used so little power and sleep issues had been such a pain in the neck over the decades that I left it running continuously and only let it switch off its screen and my external display after a 20 minute delay or with a hot corner. I have never looked back; no sleep issues since, no using Gigs of HD for a sleep image, no delay in waking or for anything else. My M3 MacBook Pro is set up the same. On a recent trip, I closed the lid with the battery at 100%, stuck in in a bag, took a flight, arrived home after 6 hours, opened the lid and the battery level was - 100%.
I exploit the 24hr running by programming backups, local and online, to happen overnight and try to keep it busy with updates, downloads, diagnostics or whatever most of the time when I’m not present - it should work for a living! None of this “sleep” nonsense…
So for those with M-series Macs, sleep is completely redundant IMHO. That’s a tremendous achievement that Apple has wrought.
For Intel Macs, if the computer is asleep, it should only wake for:
Power Nap, if turned on
Wake On Lan (or Wake On WiFi)
Key pressed on a keyboard
Mouse click
Scheduled wake (which can be set by any application)
Open lid on a laptop Mac
On Apple Silicon Macs, Power Nap is always on, so they’re going to wake periodically.
Now the question I have is about keyboard and mouse activity. That implies that any HID USB attached device can wake the computer, but it will also wake when I press a key on a Bluetooth connected Apple Keyboard. Does this mean any USB or Bluetooth device can wake the computer? Or just HID devices?
Also, my elderly aunt has a new-ish Apple Silicon iMac, and it drives her crazy that the screen turns on spontaneously in the middle of the night. She thinks someone is hacking the computer.
I’m pretty sure any USB device can wake the computer. Of course, not all should, but there’s a lot of low quality devices out there that do things they shouldn’t.