I have a 2006 Macbook running Snow Leopard. I suddenly noticed that my computer's battery would be at a different level when I woke it up than it was when I closed the lid to put it to sleep. After leaving it on a table next to my bed a few times, I realized that my computer was randomly waking up (evidenced by the Apple logo lighting up) when it was laying on a flat, level surface with nothing on top of it or anything touching it. I tried switching the settings so that I have to click the "sleep" option in the menu rather than relying on it to automatically go to sleep when the lid is closed, but the problem persists. Why won't my Macbook stay asleep?
Macbook doesn’t stay asleep when lid is closed
macbook prosleep-wake
Related Solutions
Macs will wake up in response to many hardware events. Changing a USB/Firewire/Thunderbolt cable or even plugging in / powering on a connected device will wake Macs that are sleeping. Keyboard presses, clamshell sensor detecting an open of the display lid will also wake up a sleeping Mac. These are pretty well known and obvious, even if you don't realize a pet or power fluctuation can cause a wake event.
Two software items will also wake a sleeping mac and both rely on the power management / system management controller. Both are seen in the Energy Saver preference pane. This is how applications can do the same thing as hardware and wake your mac.
For macs with a battery - the power adapter needs to be connected and powered for much of this to work. The Wake for network access is both the standard WakeOnLan (WOL) as well as Apple's Bonjour Sleep Proxy. I like the article About Wake on Demand that explains how Apple has extended the concept of WOL and made a service.
If you disable these two items - software can no longer wake your sleeping mac and you can know if it's a hardware event or a software event. The other answers go into how to look at the logs to know which event has made a specific wake up request. Hopefully this helps frame the bigger picture of how your mac can take a cat nap with one eye open.
It is possible to determine what caused the system to wake
- Open Console (/Applications/Utilities/Console)
Set the search filter to 'wake'
You're looking for the latest entry that has something like this:
Wake reason = EC LID0(In the example above, opening the display clamshell caused the machine to be woken)
Here's a list of wake 'reasons' from OSXDaily
This should shed some light on what is waking the machine, then you can go from there.
Best Answer
One possible cause is that the sensor to detect lid opening can trigger by mistake. If so, you can disable it by going into Terminal.app and typing:
Note that this means the Mac will no longer automatically wake when you open it. Instead you would need a key press or mouse click to wake.