How to Disable App Nap Completely in Mac OS X

App Nap is an energy feature introduced to the Mac in OS X Mavericks that causes inactive applications to go into a paused state, helping to reduce power usage. The feature can help to prolong battery life for the MacBook line, and it can also make an impact on overall energy usage from the computer. Though App Nap has it’s perks, some advanced users may find it to be a nuisance in some situations, and thus disabling the App Nap functionality could be desirable. We’ll show you how to quickly disable the App Nap feature everywhere in Mac OS X in one fell swoop, without having to disable it on an individual app basis.

To be perfectly clear, this disables the App Nap feature entirely and system wide, meaning for every single application and process that will run on the Mac. Essentially this returns the app behavior to what it was like pre-Mavericks, where inactive idle apps do not enter into a sleeping paused state. If you’d rather just turn it off for a single app, use this instead to accomplish that.

Disable App Nap System Wide in Mac OS X

Turning this off may impact every task, process, or application that runs in the background of Mac OS X:

1. Open the Terminal app, found in the /Applications/Utilities/ folder
2. Copy and paste the following defaults string into the terminal, then hit the return key:

defaults write NSGlobalDomain NSAppSleepDisabled -bool YES

3. Close out of Terminal and relaunch apps and/or processes for the change to carry through

Like other defaults command strings, there is no confirmation. For changes to take effect, you must relaunch all running apps. You can do that yourself by quitting and re-opening things, or by using our DIY Quit All Apps tool crafted from Automator to make quick work of this process. Rebooting the Mac will also work fine, so if you’re overdue for a system update or restart anyway it may be a good opportunity.

Once apps have been relaunched or the Mac restarted, you can confirm that App Nap is not working by backgrounding a couple of processes or hiding inactive applications for 30 minutes or so, and then checking the “Energy” panel in Activity Monitor. Look under the “App Nap” sort section and everything will be listed as “No” including the app that was backgrounded.

This is really an advanced setting to toggle off and most users should leave this feature turned on, specifically because it benefits those concerned about energy usage or maintaining the longest battery life possible.

Re-Enable App Nap in Mac OS X

Decided you’d rather have App Nap left on so that Mac OS X can manage the energy usage of applications and processes? You can easily reverse course and re-enable the App Nap feature everywhere in Mac OS X just by changing the defaults string a bit, here’s how:

1. Back in Terminal app, use the following command string and then hit return:

defaults delete NSGlobalDomain NSAppSleepDisabled

2. Quit and relaunch all apps, or reboot the Mac for the default setting to return

Again, there’s no confirmation, but App Nap will function again as intended. This feature requires OS X 10.9 or newer to use.

Heads up to a MacWorld reader for discovering the defaults command, you’ll notice it’s actually the same defaults string as that to disable App Nap for a specific app, except that “NSGlobalDomain” is used rather than an application name. Excellent find!