How to use Apple Hardware Test (ATH) on your Mac?

Apple Hardware Test (AHT) is a set of diagnostics that test your Mac’s hardware for issues.

When you detect a hardware issue on your Mac, Apple Hardware Test can be used to help you decide which hardware component is likely to trigger the problem.

Important! In case your Mac is newer than June 2013, use Apple Diagnostics for this purpose.

How to use Apple Diagnostics to test your Mac for issues?

Preparation steps:

1. Switch your Mac off.

2.  Detach all external equipment from your Mac. Keep only the mouse, keyboard, display, AC power connection and the Ethernet connection.

3. Place your Mac on a flat and stable surface. Make sure that it has a good ventilation to prevent heating.

Run Apple Diagnostics:

For Mac computers with Apple silicon:

• Switch on your Mac and hold the power button while the computer starts.
• When the startup options window appears (you should see a gear icon labeled Options), release the power button.
• On your keyboard, press Command (⌘)-D.

For Mac computers with Intel processor:

• Switch on you Mac and keep the D key on your keyboard as the computer starts up.
• Release the key when you see a progress bar or when a language needs to be selected.

Check the results from the test:

When the Apple Diagnostics is complete, you will see one or more reference codes with identified issues.

If you want to run the test again, click on “Run the test again”.

If you want to restart your Mac, click on the “Restart” option.

If you want to shut down, click on the “Shut down” option.

If you want to get more details regarding the detected issues and the solutions available, firstly check if your Mac is connected to the internet. Then, click on the “Get started” option. The computer will restart to a support webpage that contains more information. When you are done reading the support webpage, select “Restart” or “Shut Down” from the Apple menu.

Apple Hardware Test

1. Firstly, unplug and disconnect all external devices from your Mac, otherwise, once you run the Apple Hardware Test, it may display an error message. Keep only the keyboard, mouse, display, AC power connection, and the Ethernet connection (in case it is applicable).
2. Place your Mac computer on a flat and hard work surface that allows for good ventilation before you run the ATH.
3. Then, shut your Mac down.
4. Next, turn the Mac on and press and hold the D key on your keyboard while it is loading. Keep the D key pressed down until the Apple Hardware Test icon appears on the screen.
5. From the languages that are available pick your language and then click on the right arrow. Use the up and down arrows from the keyboard if you aren’t using a mouse. Next, press the Return key.
6. To start the testing process, click on the Test button. You can do the same by pressing the T key or the Return key from the keyboard. If you want to run a more thorough test, choose the “Perform extended testing” option. This may take some time but performs a more comprehensive examination.
7. Wait for the test process to complete and when that happens, you will see the results in the bottom-right section of the window.
8. Press Restart or Shut Down at the bottom of the window to exit Apple Hardware Test.

More details for OS X Lion V10.7 or later and MacBook Air (late 2010):

• Some Mac computers with OS X Lion v10.7 or later will launch AHT from the Internet, especially if the startup disk does not include AHT. ATH can also be launched if you hold down Option and D keys from the keyboard at startup. You will need an Internet connection through Ethernet or Wi-Fi for this.
• Users who use the OS X Lion v10.7 or earlier and cannot launch ATH should check if they have an OS X installation disk named “Applications Install Disk 2”.  This disk needs to be inserted in the optical drive (be it internal or external) before the steps above are applied.
• For MacBook Air (late 2010) users, simply plug the MacBook Air Software Reinstall thumb drive into the USB port.