How to use Apple Hardware Test on your Mac
Apple Hardware Test (AHT) contains a suite of diagnostics that can test the hardware of your Mac.
After isolating an issue on your Mac to a probable hardware issue, you can use Apple Hardware Test to help determine which hardware component may be causing the issue.
If your Mac was introduced after June 2013, follow the steps for using Apple Diagnostics instead.
How to use Apple Hardware Test
Disconnect all external devices except keyboard, mouse, display, Ethernet connection (if applicable) and connection to mains power. Apple Hardware Test may display an error message if you don't disconnect all other devices.
Make sure your Mac is on a hard, flat, stable, well-ventilated work surface.
Shut down your Mac.
Turn on your MacNo alt supplied for Image
Select your language and click the right arrow. If you're not using a mouse, you can use the up and down arrows to select a language, then press the Return key.
To start testing, click the Test button, press T or press Return. Optionally select "Perform extended testing" before starting the test. This will perform a more thorough test that takes longer to complete.
When the test has been completed, review your test results in the bottom right-hand section of the window.
To quit Apple Hardware Test, click Restart or Shut Down at the bottom of the window.
Learn more
Some Mac computers that came with OS X Lion v10.7 or later will start up from AHT over the internet if your startup disk doesn't contain AHT, or if you hold down Option-D during the startup process. This requires an internet connection over Ethernet or Wi-Fi.
If you're using OS X Lion v10.7 or earlier and you can't get AHT to start, see if you have an OS X installation disc named "Applications Install Disc 2". Insert the disc in your internal optical drive or external Apple SuperDrive before following the steps above. Or, if you're using a MacBook Air (Late 2010), plug the MacBook Air Software Reinstall USB drive into your USB port instead.
