Mac OS X: How to reinstall a prior version

This document explains how to correctly reinstall a prior version of Mac OS X in the event that other troubleshooting does not resolve an issue.

Before reinstalling an earlier version of Mac OS X to resolve an issue, make sure you have tried other troubleshooting steps.

This article has been archived and is no longer updated by Apple.

Note: You should not attempt to install or reinstall a version of Mac OS X earlier than what came with your computer.

Mac OS X v10.2, 10.3, 10.4, 10.5 or later

You can perform an Archive and Install feature, which reinstalls Mac OS X without erasing the volume.

Important: You should only perform an Archive and Install installation over the same major version (reference release) of Mac OS X. For example, if your Mac OS X Install disc has Mac OS X 10.4, then you should only perform an Archive and Install over version 10.4 through 10.4.11. "Downgrading" your operating system version to an earlier reference release may lead to issues. For example, performing an Archive and Install installation with Mac OS X 10.3.9 or earlier Install discs over a Mac OS X 10.4.11 installation could lead to issues such as these:

  • Some applications may not work following an Archive and Install installation. (You have newer versions, but older frameworks.)
  • User account settings may not be as expected, including password formats, default groups, and default helper user accounts.
  • Some data formats, such as Mail databases, may not be backwards compatible.

If you intend to reinstall an earlier major release, you should back up your important data and perform an erase install instead of using Archive and Install.

Mac OS X v10
.0 through 10.1.5

    1. Erase the Mac OS X volume before installing. Because erasing a volume means deleting all files on it, you should first back up important data to a different disk. See this article for specific instructions and warnings about the reinstallation process.
    2. Install Mac OS X.
    3. Use Software Update to install available Mac OS X updates.
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