If your computer is waking up from sleep without any intervention from you, it's probable another program or device is waking it up. Here's how to find out what woke it up last.
We've shown you how to find out what's keeping your computer from going to sleep, but if your computer keeps waking up after you put it to sleep, there's a similar solution.
For Windows: If your computer is waking up regularly, finding the culprit can be tough — but finding the most recent wake cause is a good place to start. To do that, go to Start > Programs > Accessories, right-click on Command Prompt, and open it as an administrator. Then type:
The output will tell you what woke up your computer last, which — if you didn't initiate it yourself — is probably your culprit.
Sometimes, unfortunately, this process doesn't give you quite enough information to deduce the problem, so you have to look elsewhere. Often, it's a result of a "wake timer", which can be a program, schedule task, or other item that's set to wake up your computer when it runs. You can disable wake timers in Windows' Power Options. You may also find that your mouse or keyboard is waking up your computer even when you don't touch them. For full instructions on how to dig deeper and fix these problems, check out this article at the How-To Geek.
For Mac: If you want to find out what woke up your Mac at a specific time, you can usually find it logged in the Console app. Head to /Applications/Utilities, open up Console, and search for:
You should see a list of the last few wakes, and the reasons they were triggered. If you aren't sure what one of the reasons means, check out this glossary from CNET for more information.
How To Prevent Your Computer From Waking Up Accidentally [How-To Geek]