Before you start
Apple's checklist (Apple, Use Apple Diagnostics to test your Mac):
- Install any macOS updates if you can.
- Disconnect everything except the keyboard, mouse, display, Ethernet cable if you use one, and the power adapter. An external drive or hub left plugged in can muddy the result.
- Put the Mac on a hard, flat surface with good ventilation.
- Keep a laptop plugged in. One of Apple's reference codes means the battery was too low to finish the test.
- Have Wi-Fi ready on macOS 26 or 27. Apple lists an internet connection as a requirement for the newer version (Apple, Apple Silicon Mac: Apple Diagnostics for Repair).
Not sure which chip you have? Apple menu › About This Mac shows Chip followed by an Apple M-series name on Apple silicon; an Intel Mac shows Processor instead.
Start Apple Diagnostics
The keys are the same on macOS 15, 26 and 27:
- Shut down from the Apple menu, and wait until the screen is black. If the Mac won't shut down, press and hold the power button until it turns off.
- Press and hold the power button (the Touch ID button on a MacBook with Touch ID). Keep holding until Loading startup options or the Options icon appears, then let go.
- Press and hold Command-D until the Mac restarts into diagnostics.
On an Intel-based Mac, Apple's steps are different: turn the Mac on and immediately press and hold the D key, or Option-D if that doesn't work.
What you see next depends on the version of macOS installed.
On macOS 15: the automatic test
On a Mac with macOS 15 Sequoia, Apple Diagnostics may ask you to choose a language or a network, and then tests the hardware on its own; the onscreen steps vary by Mac model. If you're offline and shown terms and conditions, Apple says you may be offered Run Offline. When it finishes, it shows the results, with a reference code for anything it found (Apple).
Write the codes down or take a photo of the screen. Eclectic Light, which tracks these tools closely, notes that results from this older version also appear later under Diagnostics in System Information, while results from the newer tool on macOS 26 and 27 don't (Eclectic Light, February 2026). Restart the Mac to leave diagnostics.
On macOS 26 and 27: Diagnostics & Repair
From macOS 26 Tahoe, Apple's article says you choose a specific test, such as one for the display, keyboard or trackpad, where earlier versions ran automatically. Command-D now opens a screen called Diagnostics & Repair, which also handles the checks Apple documents for after a repair (Apple):
- Continue past the Diagnostics & Repair screen.
- Choose a Wi-Fi network if you aren't on Ethernet, and accept the terms.
- Choose Run Diagnostics and pick a test suite from the list.
- Read the result for that suite, then run the next one you need.
Apple's list of suites, and which Macs get each:
| Suite | What it checks | Available on |
|---|---|---|
| Mac Resource Inspector | A quick check that the main hardware is present and working. The best first test | Laptops, desktops and iMac |
| Display Anomalies | Shows colors and patterns so you can spot bad pixels or debris | Laptops and iMac |
| Keyboard | Every key, the backlight and the Caps Lock light | Laptops |
| Trackpad | That every area of the trackpad responds | Laptops |
| Touch ID | The fingerprint sensor | MacBook Neo models with Touch ID, per Apple's list |
| Audio | Plays test tones; Apple warns they're loud. Headphones are needed to test the headphone jack | Laptops, desktops and iMac |
| Battery Drain Tool | Drains the battery to a set level and plays a tone when done. A repair step, not a health test | MacBook Air (M5) and MacBook Pro (M5, M5 Pro, M5 Max) |
Two practical notes from Eclectic Light's testing: the suites run one at a time, with no way to run them all in sequence, and Mac Resource Inspector took between one and seven minutes. Each result shows a check mark, a warning or an error symbol, with details behind its ⓘ button. Leave the Battery Drain Tool alone unless a repair needs it: it does exactly what its name says.
What the reference codes mean
Apple publishes the full list (Apple, Apple Diagnostics reference codes). The ones people most often look up, in Apple's terms:
| Code | Meaning |
|---|---|
| ADP000 | No issues found |
| PPT001 | Battery not detected |
| PPT002, PPT003 | Battery will need replacing soon; it works but holds less charge than when new |
| PPT004, PPT006 | Battery requires service; it isn't working normally, even if you haven't noticed |
| PPT005 | Battery isn't installed properly. Apple says to shut down and stop using the Mac |
| PPT007 | Battery needs replacing; it holds significantly less charge than when new |
| PPT021 | Battery too low to finish the test: plug in and run it again |
| PPP001 to PPP008, PPP020 | A possible problem with the power adapter, or no adapter detected |
| PPF001, PPF003, PPF004 | A possible problem with the fan |
| PPM002 to PPM016 | A possible problem with the onboard memory |
| VDH001 to VDH004 | A possible problem with a storage device |
| VFD001 to VFD007 | A possible problem with the display or graphics processor |
| NDK, NDR, CNW, NDL codes | Keyboard, trackpad, Wi-Fi and Bluetooth hardware respectively |
For a few codes, Apple suggests simple steps first, such as running the test again or trying a different power adapter or accessory. For the rest, Apple's advice is to take the code to an Apple Store, an Apple Authorized Service Provider or an Independent Repair Provider. If your MacBook says "Service Recommended" for the battery as well, what Service Recommended means covers the options and costs.
What a clean result does and doesn't prove
ADP000, or a row of check marks, means the tests that ran found nothing. It doesn't cover software, and a fault that comes and goes may not show up during a short test. If the problem continues after a clean result:
- Unexpected restarts: what to do when your Mac restarted because of a problem.
- Slowness, freezes or apps misbehaving: start up in safe mode to rule out software that loads at startup.
- A MacBook that won't charge: MacBook not charging when plugged in separates settings from faults.
- Battery wear: Diagnostics flags a battery that needs service, but the gradual picture comes from Maximum Capacity and cycle count; how to check battery health shows where to find them.
How Tend helps
Diagnostics is a snapshot taken on one day. Tend's free Battery page shows the battery's health, cycle count and how much of its rated cycle life is used whenever you look, and Tend Pro keeps a daily health record, so you can see whether capacity slid slowly or dropped suddenly, which is useful to mention when you book a repair.
Questions
How do I run diagnostics on a MacBook with Apple silicon?
Shut down. Press and hold the power button (the Touch ID button on laptops) until the startup options appear, release it, then press and hold Command-D until the Mac restarts into diagnostics. Disconnect everything except the keyboard, mouse, display, Ethernet and power first.
What does ADP000 mean?
ADP000 is Apple Diagnostics' code for no issues found. It means the tests that ran didn't find a hardware fault. It doesn't rule out a software problem, or a fault that only appears now and then.
Why can't I run all the tests at once on macOS 26?
On Macs with Apple silicon running macOS 26 or 27, Command-D opens Diagnostics & Repair, where you choose one test suite at a time, such as Mac Resource Inspector, Display Anomalies or Keyboard. Apple's documentation lists the suites separately, and there's no option to run them all in sequence.
Does Apple Diagnostics need an internet connection?
On macOS 26 and 27, Apple lists a Wi-Fi or wired connection as a requirement and asks you to choose a network before you start. On macOS 15, Apple says you may be offered a Run Offline option if you're shown the terms and conditions.
Can Apple Diagnostics check my battery health?
It can report battery problems with PPT reference codes, such as a battery that needs replacing or isn't detected. For day-to-day wear, the Maximum Capacity and cycle count in System Settings and System Information tell you more.
Related guides
Mac maintenance on Apple silicon: what still matters
Which checks are worth doing, and when
How to check your MacBook's battery health
Maximum Capacity, cycle count and what they mean
“Your computer restarted because of a problem” on Mac
When the Mac restarts on its own
MacBook not charging when plugged in? Causes and fixes
Before you blame the battery or the adapter
More detailed guides:
Sources
- Apple, Use Apple Diagnostics to test your Mac
- Apple, Apple Silicon Mac: Apple Diagnostics for Repair (21 September 2026)
- Apple, Apple Diagnostics reference codes
- Eclectic Light, Last Week on My Mac: Repair Assistant has replaced Diagnostics (February 2026, third party)
Watch your battery between tests
Tend is free to download. Pro is $1.99 a month, $12.99 a year with a 7-day free trial, or $29.99 once.