All Macs can use the version of Mac OS X that was originally included with them, as well as later updates from Software Update, and compatible retail Mac OS X upgrades.
Restoring (reinstalling) Mac OS X using the correct Restore DVD
When restoring Mac OS X, you should always use the Mac OS X Restore DVD which was originally included with the Mac. If a major reference release of Mac OS X is released after the individual Mac has been released, and, that model of Mac is listed as supported on the box or product requirements, then the newer reference release DVD may be used to install a later Mac OS X version. An example of this would be using a retail version of Mac OS X v10.6 Snow Leopard on an Intel-based Mac that originally shipped with Mac OS X v10.5.x, after confirming that model of Mac is supported by Mac OS X v10.6.
Important: Do not use an earlier retail version of Mac OS X, or a later version that is not supported on the Mac you are restoring. Always check the specifications on the DVD box or our support site, and check for your model of Mac before using a retail DVD version of Mac OS X to restore the operating system. If you have any doubt, you should use the restore DVDs which originally came with the Mac–consult the chart in this article. (If you have a PowerPC-based Mac that was produced after Jan 1, 1998, see this article instead.) For example, if your Mac shipped with Mac OS X v10.6.3, you should not use a Mac OS X v10.5.6 Restore DVD with it.
Restoring Mac OS X using Time Machine
If you restore your system from a Time Machine backup, you should only restore a backup which was either made by your Mac, or by a Mac with identical hardware. (Mac OS X v10.6.3 or later alerts you if your hardware is not the same as the Mac that made the backup.) If you restore a Time Machine backup from a different kind of Mac, your Mac may not start up, or may have various other issues related to missing resource files that cannot be corrected by using Software Update.
If your Mac is a different model than the Mac that made the backup you want to restore, you should use Setup Assistant on the new Mac first, connect Time Machine backup drive as described in Setup Assistant, and then choose the option to move your user account(s) to the new Mac.
Installing an earlier version of Mac OS X?
You should never install a version of Mac OS X that's older than the version that your Mac originally shipped with. For more information, read this article.
Questions and answers
- I do not have the restore media that originally shipped with my Mac, what should I do?
Contact AppleCare and request replacement of the correct restore media.
- I have a MacBookAir (Mid 2010) and do not see a restore DVD in the box.
MacBook Air (Mid 2010) includes a small, white USB Software Reinstall Drive instead of a DVD. Ensure that the USB drive is plugged in with the gold contacts facing upwards.
- Why is some of the additional content that would normally be on a Restore DVD not on my MacBook Air (Mid 2010)'s USB Software Reinstall Drive?
Nearly all the content is available online. See this article for more information.
- I want to install an older version of Mac OS X. Is it OK to do this if the installer doesn't alert me about any issues?
You should never install a Mac OS X version that is earlier than what was originally included with the Mac. You can go forward in software versions using Software Update, but you should not go backwards in versions.
- I need to relocate the operating system and data on my iMac or Mac Pro (Mid 2010) to another storage device, how do I do this?
You can easily do this with Disk Utility. Follow the steps in this article for more information.
- I think my Mac is having an issue that was caused by installing an unsupported or incorrect version of Mac OS X on it. What's the quickest way to diagnose and resolve this issue?
Start up from a removable USB drive or external FireWire drive that has a compatible version of Mac OS X on it. If the issue persists, try a Safe Boot with starting from the same media. Also, if you suspect a hardware issue, you can hold the "D" key during startup to use Apple Hardware Test.