Apple Diagnostics checks your Mac’s internal hardware for possible problems with components such as memory, the logic board, battery, and wireless hardware. It can help you determine whether a startup problem is likely caused by hardware rather than software.
Quick Answer
To run Apple Diagnostics:
- Shut down your Mac and disconnect all external devices except the keyboard, mouse, display, Ethernet connection, and power.
- Start the Mac and use the appropriate method:
– Mac with Apple silicon: Press and hold the power button until startup options appear, then press and hold Command (⌘)-D.
– Intel-based Mac: Turn it on and immediately press and hold D. - Follow the onscreen instructions.
- Write down any reference code, then select an available option to restart, shut down, or get more information.
Apple Diagnostics can identify suspected hardware faults, but it does not repair them and may not detect every problem.
What Apple Diagnostics Does
Apple Diagnostics is a built-in hardware test for Mac computers. It checks selected internal components and displays a reference code if it finds a potential issue.
The test can be useful when your Mac:
- Turns off unexpectedly
- Restarts without warning
- Fails to start normally
- Shows a blank screen
- Runs unusually slowly because of a hardware problem
- Has battery, memory, or wireless issues
- Produces unusual fan, startup, or hardware behavior
Apple Diagnostics is not a general-purpose performance test. It does not remove malware, repair macOS, recover deleted files, or fix damaged applications. A result indicating that no problems were found also does not guarantee that every component is working perfectly.
Prepare Your Mac for the Test
Before starting, save your work and close your apps if possible. Apple Diagnostics requires a restart or shutdown, so unsaved changes may be lost.
Follow these preparation steps:
- Save open documents. Make sure files are saved locally or synchronized as needed.
- Connect the power adapter. A desktop Mac should be connected to power. A Mac notebook should be connected to its charger when possible.
- Disconnect most external devices. Remove external drives, USB hubs, printers, cameras, docks, memory card readers, and other accessories.
- Keep essential devices connected. You can generally leave a keyboard, mouse, display, Ethernet connection, and power connected.
- Note the problem you are investigating. Record what happened, when it started, and whether the issue is repeatable. This information can help a technician interpret the result.
- Have an internet connection available. Apple Diagnostics may offer additional information or support options that require the internet.
If your Mac is frozen and will not shut down normally, press and hold the power button until it turns off. This can cause unsaved work to be lost, so use it only when normal shutdown is unavailable.
Run Apple Diagnostics on a Mac with Apple Silicon
These instructions apply to Macs with Apple silicon, including M-series processors.
- Shut down your Mac. Select Apple menu > Shut Down, then wait until the screen is completely off.
- Press and hold the power button.
- Continue holding the button until you see the startup options window.
- Release the power button.
- Press and hold Command (⌘)-D on the keyboard.
- Release the keys when Apple Diagnostics begins.
- Follow the onscreen instructions.
Depending on the Mac and the detected problem, Apple Diagnostics may ask you to select a language or connect to a network. Complete those prompts if they appear.
When testing finishes, the screen may show a reference code. Write it down exactly, including letters and numbers.
If Startup Options Do Not Appear
Make sure the Mac is fully shut down before trying again. If it immediately starts normally, shut it down and repeat the process, holding the power button continuously until the startup options screen appears.
If you use a wireless keyboard, connect it to the Mac with a cable if possible. A wired keyboard can make it easier for the Mac to recognize the Command-D shortcut during startup.
Run Apple Diagnostics on an Intel-Based Mac
Use these instructions if your Mac has an Intel processor.
- Shut down your Mac. Select Apple menu > Shut Down, then wait for the Mac to turn off.
- Press the power button.
- Immediately press and hold the D key.
- Continue holding D until a progress bar appears or you are asked to choose a language or connect to a network.
- Follow the onscreen instructions.
- Record any reference code displayed when testing is complete.
If holding D does not start the test, restart the Mac and immediately hold Option-D instead. This alternate shortcut may start Apple Diagnostics over the internet when the local diagnostic software is unavailable.
If You Use a Wireless Keyboard
A wireless keyboard may not connect quickly enough during startup. If possible, use a built-in keyboard on a Mac notebook or connect an external keyboard directly to the Mac. Avoid connecting the keyboard through a hub or dock while starting the test.
Understand Apple Diagnostics Results
Apple Diagnostics may display a message stating that no problems were found, or it may provide one or more reference codes.
When No Problems Are Found
A result indicating that no problems were found means the test did not identify a hardware fault within the areas it checked. It does not prove that the Mac is free of all problems.
Software, settings, corrupted files, incompatible peripherals, intermittent failures, and problems that do not occur during the test may not be detected. If the symptoms continue, continue troubleshooting or contact Apple or an authorized service provider.
When a Reference Code Appears
A reference code identifies the general area of a possible hardware problem. Common code families include:
| Code family or example | General indication |
|---|---|
| ADP000 | No issues found |
| CNW001–CNW008 | Possible wireless hardware issue |
| NDC001–NDC006 | Possible camera issue |
| PFR001 | Possible firmware issue |
| PPF001–PPF007 | Possible fan issue |
| PPM001–PPM007 | Possible memory or logic-board-related issue |
| PPP001–PPP003 | Possible power adapter issue |
| PPT001–PPT007 | Possible battery issue |
| VFD001–VFD007 | Possible display-related issue |
| VFF001 | Possible audio hardware issue |
These codes are general reference categories, not complete diagnoses. The exact meaning can vary by Mac model and test result. Write down the entire code and show it to Apple Support or a qualified technician.
Do not replace a component based only on a code unless a qualified service provider confirms the diagnosis. A code may point to a broader hardware area rather than one user-replaceable part.
What to Do After the Test
After Apple Diagnostics finishes, use the result to choose your next step.
If No Issue Is Found
If your Mac still has problems:
- Restart the Mac normally.
- Reconnect external accessories one at a time. A particular accessory, cable, or dock may be causing the problem.
- Check whether the issue occurs in more than one app or user account.
- Install available macOS updates through System Settings > General > Software Update.
- Run Apple Diagnostics again if the problem is intermittent.
- Contact Apple Support or an authorized service provider if the symptoms continue.
Do not erase the Mac or reinstall macOS solely because Apple Diagnostics reports no hardware problem. Those actions can remove data or change the system without addressing the actual cause.
If a Hardware Code Appears
- Record the code exactly.
- Record the Mac model and serial number if available.
- Note the symptoms that led you to run the test.
- Back up important files before service whenever the Mac can still start normally.
- Contact Apple Support or an authorized service provider.
- Provide the reference code and describe what happened before the test.
If the Mac cannot start, makes unusual sounds, becomes extremely hot, or shows signs of a damaged battery, stop using it and seek professional help. Do not open the Mac or attempt a battery repair unless you are qualified to do so.
If Apple Diagnostics Offers Support Options
Apple Diagnostics may provide options to restart, shut down, view more information, or contact support. Choose the option that matches your situation. If you need service, keep the reference code available when speaking with Apple Support.
Troubleshooting Apple Diagnostics
Apple Diagnostics Does Not Start
Verify that you are using the correct startup method:
- Apple silicon: hold the power button until startup options appear, then hold Command-D.
- Intel: turn on the Mac and immediately hold D.
- Intel alternative: use Option-D if the standard shortcut does not work.
Also try a wired keyboard, disconnect unnecessary accessories, and make sure the Mac is connected to power.
The Mac Starts Normally Instead
You may be pressing the key too late, releasing it too soon, or using the wrong procedure for the processor type. Shut down completely and try again. On an Apple silicon Mac, do not press D immediately after turning it on; first hold the power button until startup options appear.
The Test Cannot Connect to the Internet
If Apple Diagnostics asks for a network, select an available Wi-Fi network and enter its password. If Wi-Fi is unavailable, connect Ethernet if your Mac supports it directly or through a compatible adapter.
If the test still cannot connect, try again later or use the local startup method when available. A network problem does not necessarily mean that the Mac has a hardware fault.
The Test Freezes or Stops
Wait several minutes first, especially if a progress bar is moving. If nothing changes and the Mac does not respond, press and hold the power button until it shuts down. This may cause unsaved work to be lost, but it may be necessary when the test is unresponsive.
Reconnect power, disconnect nonessential accessories, and run the test again. If it repeatedly stops at the same point, record what happened and contact Apple Support.
The Mac Shuts Down During Testing
Connect the power adapter and repeat the test. A low battery, faulty adapter, power connection, or hardware problem may interrupt the process. If the Mac repeatedly shuts down even when connected to power, arrange service.
Frequently Asked Questions
Does Apple Diagnostics check software?
No. Apple Diagnostics primarily checks hardware. It does not fully diagnose macOS, applications, user accounts, malware, or damaged documents.
Can Apple Diagnostics repair my Mac?
No. The tool reports possible hardware problems and may provide support options. It does not repair or replace components.
How long does Apple Diagnostics take?
The duration varies by Mac model, hardware condition, and whether the test needs an internet connection. Allow enough time for the test to complete without interrupting it.
Can I run Apple Diagnostics without an internet connection?
The test may run locally without internet access, but some diagnostic or support features may require a network connection. If the Mac asks you to connect, use Wi-Fi or Ethernet when possible.
Will Apple Diagnostics delete my files?
Running the test is not intended to erase your files. However, shutting down a frozen Mac or performing other recovery steps can cause unsaved work to be lost. Always back up important data before service or major troubleshooting.
Should I run the test more than once?
You can repeat the test if the first attempt was interrupted or if the problem is intermittent. If the same reference code appears repeatedly, provide all results to Apple Support or a service provider.
Is Apple Diagnostics the same as Apple Hardware Test?
Apple Diagnostics is the newer name for Apple’s built-in Mac hardware testing tool. Older Intel-based Macs may refer to similar functionality as Apple Hardware Test, but the startup process and available results can vary by model.
What should I do with the diagnostic code?
Write it down exactly and give it to Apple Support or an authorized service provider. The code helps identify the general hardware area that may need further evaluation.
Final Thoughts
Apple Diagnostics is a useful first step when you suspect a hardware problem with your Mac. Use the Apple silicon or Intel startup method that matches your computer, disconnect unnecessary accessories, save your work beforehand, and record any reference code. Treat the result as guidance rather than a complete diagnosis, especially if the Mac continues to show symptoms after the test.