App Nap: Does It Slow Down Your Mac?
Understanding App Nap on macOS
Introduced to macOS in 2013, App Nap is a system feature that often goes unnoticed. It’s perfectly understandable if you’re unaware of its function even years after its implementation.
How App Nap Works
Essentially, App Nap conserves system resources by placing applications that are not in active use into a low-power state. This prevents them from consuming CPU cycles and other resources when they aren't being directly interacted with.
Consider a scenario with numerous open windows – perhaps twenty or more. App Nap ensures that only the applications currently in focus are actively utilizing system resources and impacting battery life. This results in measurable energy savings.
App Nap vs. Power Nap: Key Differences
It's important to distinguish App Nap from Power Nap, another macOS feature with a similar-sounding name. While both aim to optimize energy usage, they operate independently.
Power Nap enables your Mac to perform tasks such as downloading software updates or creating system backups while in sleep mode. These two features address different aspects of power management and are not interconnected.
In short, App Nap manages active applications, while Power Nap handles background tasks during sleep.
Understanding App Nap Functionality
Introduced with macOS 10.9 Mavericks, App Nap represents a key energy-saving feature. Alongside this, a utility displaying "Apps Using Significant Energy" was integrated into the battery icon.
Essentially, App Nap functions as a system optimization, preventing applications that are not actively in use from consuming CPU cycles and other valuable system resources. This contributes to improved battery performance and overall system responsiveness.
Criteria for App Nap Activation
According to Apple’s documentation for developers, App Nap is initiated only when an application meets specific conditions:
- It is not the currently active, foreground application.
- The visible area of its window hasn't been recently refreshed with new content.
- No audio output is currently being produced by the application.
- The application hasn't requested any special power management privileges.
- It is not actively utilizing OpenGL for graphics rendering.
What implications do these criteria have? Firstly, the application you are presently interacting with will remain unaffected. Similarly, any application with a visible window that is actively updating its display will not be subject to App Nap.
Applications that are currently playing audio are also exempt, ensuring uninterrupted background music or podcast playback. The core principle is to minimize resource usage by applications that aren't actively providing a service to the user.
Upon reactivation – when you bring an application’s window to the forefront – it resumes normal operation. This process is designed to be seamless and should not introduce any performance degradation, but rather free up resources for the applications you are actively using.
Determining if an Application is Utilizing App Nap
Related: Troubleshooting Mac Issues Using Activity Monitor
App Nap isn't typically a feature directly visible to the user. There isn't a visual cue, such as an icon on the Dock, to indicate when an application is currently in a napping state. To ascertain this, the Activity Monitor must be accessed, located within Applications > Utilities, or via a Spotlight search.
Navigate to the "Energy" tab within Activity Monitor. A column labeled "App Nap" will be displayed. An entry of "Yes" in this column signifies that the corresponding application is presently napping.
Activating the application will immediately terminate the nap, and the Activity Monitor will then display "No" in the "App Nap" column. The system is designed for these transitions to be seamless and unnoticeable to the user.
However, if you suspect App Nap is impacting application performance, options are available to address this potential slowdown.
Disabling App Nap: A Comprehensive Guide
App Nap is a system-wide feature that impacts all applications, irrespective of their original design. This universal application of the function can potentially introduce issues with older software, possibly hindering background processes or causing performance degradation.
If you suspect App Nap is contributing to problems, a straightforward verification method exists.
How to Disable App Nap for Individual Applications
Begin by locating the application within Finder. Subsequently, right-click on the application icon to access a contextual menu.
Select "Get Info" from the menu. Within the information window, examine for the "Prevent App Nap" option.
This option isn't universally available for all applications. It typically appears for software not specifically engineered with App Nap compatibility. Our observations suggest this primarily affects applications developed in 2013 or earlier, although exceptions do occur.
If the option is present, enable it and assess whether the issue is resolved.
Globally Disabling App Nap via Terminal
Alternatively, App Nap can be entirely disabled using a Terminal command. Access the Terminal application, found within Applications > Utilities, or via Spotlight search.
Execute the following command:
defaults write NSGlobalDomain NSAppSleepDisabled -bool YESThis command deactivates App Nap system-wide. Should this resolve a specific application issue, it's advisable to inform the application's developer.
To re-enable App Nap after testing, use this command:
defaults delete NSGlobalDomain NSAppSleepDisabledThe Benefits of App Nap and When to Disable It
Generally, App Nap is a beneficial feature to keep enabled. The improved battery life it provides is a significant advantage, and most users won't even be aware of its operation.
However, understanding how to disable it is valuable for troubleshooting potential compatibility issues.
Image credit: Arthur Caranta/Flickr