Using Mac OS X, how do I repair permissions, and what does that do?

Mac OS X assigns specific access privileges, known as permissions, to all of your programs, folders, and documents. These permissions are usually managed automatically, but when a permissions error occurs, it can cause significant problems. For example, your applications may not launch, or your computer might respond slowly. These problems are more likely to occur after you update your operating system or install new software.

To improve your system's performance, use the permissions repair function in Disk Utility:

1. To open Disk Utility, from the Applications folder, open Utilities, and then double-click the Disk Utility icon.
   
   
2. In the column on the left, click your startup disk.
   
   
3. Click the First Aid tab, and then click Repair Disk Permissions. Disk Utility will reset any files and folders with incorrect settings.

Note: If a third-party application has permissions errors and did not use Apple's installer, a permissions repair may not fix everything. If you follow the steps above, and your application still does not launch, you may need to remove and reinstall the problematic applications. For more information on removing applications in Mac OS X, see In Mac OS X, how do I remove an application?

For more information about how permissions work in Mac OS X, see Troubleshooting permissions issues in Mac OS X in Apple's knowledge base.

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