Before you pay anyone to look at a misbehaving Mac, run the free hardware test Apple builds into every machine. Apple Diagnostics (called Apple Hardware Test on Macs from before mid-2013) checks the memory, logic board, battery, and other components in a few minutes and hands you a reference code you can quote to any repair shop. It is the single most useful thing you can do before deciding whether to repair, sell, or replace a Mac.
What Apple Diagnostics does (and does not) find
Apple Diagnostics runs a low-level self-test of the hardware: RAM, the logic board and its sensors, the battery and power system, the graphics chip, and the wireless module. When it finishes it shows one or more reference codes that tell you which subsystem, if any, failed.
It is good at catching failing memory, a bad battery, sensor and cooling faults, and gross logic-board failures. It will not find software problems (a corrupt macOS, a full startup disk, a bad kext), and it cannot test a component that is so dead the Mac will not power on at all. If your Mac shows nothing on screen and never chimes or lights up, see our guide on a MacBook that will not turn on first.
How to run Apple Diagnostics on an Apple Silicon Mac (M1, M2, M3 and newer)
- Shut the Mac down completely.
- Press and hold the power button until you see “Loading startup options.”
- Release the power button, then press Command (⌘) - D on the keyboard.
- Apple Diagnostics loads and runs automatically. It takes a few minutes.
How to run Apple Diagnostics on an Intel Mac
- Shut the Mac down, then turn it on and immediately hold the D key until a progress bar or a language picker appears.
- If holding D does not work, restart and hold Option - D instead — this loads Apple Diagnostics over the internet from Apple’s servers, which is handy if the local test files are damaged. (Internet Diagnostics needs Wi-Fi or Ethernet.)
- Let the test finish. On very old Macs (2013 and earlier) this tool is named Apple Hardware Test and looks slightly different, but the D-key startup is the same.
Reading the reference codes
When the test finishes it lists one or more codes. The one you want to see is ADP000 — that means “no issues found.” Anything else points at a subsystem. Common prefixes:
- ADP000 — no problem detected.
- PPT — battery or power-related fault.
- NDR / NDC / NDK — USB, Thunderbolt, or trackpad/keyboard controller.
- VFD / VFF — display or graphics.
- PFM / PFR — firmware / SMC.
- Codes starting with MEM — memory. On Intel Macs with removable RAM this can sometimes be fixed by reseating a module; on Apple Silicon the memory is inside the chip and a MEM fault means a logic-board repair.
You do not need to memorize the full list. Write down the exact code before you close the screen — it is the first thing any technician (Apple or independent) will ask for, and it stops you from paying for a guess. To run the test again, click Run the test again or press Command-R from the results screen.
If Apple Diagnostics finds nothing but the Mac still misbehaves
A clean ADP000 result usually means the problem is software, not hardware. Work through these in order:
- Reset the firmware settings: see how to reset NVRAM, PRAM and the SMC.
- Boot into macOS Recovery and run Disk Utility First Aid, then reinstall macOS.
- If you are chasing random restarts specifically, our kernel-panic and random-restart guide has the full fix ladder (Apple Diagnostics is step 5 there).
When the code says repair — and repair is not worth it
If Apple Diagnostics returns a memory, graphics, or logic-board code on an Apple Silicon Mac, you are usually looking at a board-level repair that costs more than the machine is worth. That is the moment to weigh a repair against a trade-in. You can get a no-obligation quote for a broken Mac through our broken-MacBook trade-in — we buy Macs with failed diagnostics and apply the value toward a working one. And if you would rather just replace it outright, our Apple clearance collection is the cheapest way into a tested, warrantied Mac.
Frequently asked questions
Is Apple Diagnostics free?
Yes. It is built into every Mac and there is no charge to run it. You only pay if the code it returns points to a repair you choose to make.
My Mac will not start the test. What now?
On Apple Silicon, make sure you fully shut down first and hold the power button (not just tap it) until the startup-options screen appears, then press Command-D. On Intel, if the D key does nothing, try Option-D for the internet version. If the Mac never powers on or shows no screen at all, the machine is too far gone for Diagnostics — treat it as a no-boot repair-or-trade decision instead.
Does a clean result (ADP000) mean my Mac is fine?
It means no hardware fault was detected. Software issues, a failing SSD that has not fully died yet, and intermittent faults can still slip past it — but a clean result is a strong sign to focus on software fixes rather than paying for hardware.
What is the difference between Apple Diagnostics and Apple Hardware Test?
They are the same idea. Apple Hardware Test is the older name used on Macs from 2013 and earlier; newer Macs call it Apple Diagnostics. The startup keys (hold D, or Option-D for internet) are the same.
Questions about a code your Mac returned? Talk to a human — tell us the reference code and the model and we will tell you honestly whether it is worth fixing.