Comprehensive hardware testing for your MacBook
Items tagged Must-Check are the essential ones to complete before closing the deal
Quick answers to the questions buyers ask most before paying for a used MacBook
Start with ownership and identity: Activation Lock is off, there is no corporate MDM enrollment, the serial number matches in three places (system, bottom case, box), Parts & Service shows no unexplained repairs, and Apple Diagnostics returns ADP000. Then the hardware deal-breakers: original display, no liquid damage, no dead pixels, working speakers, microphone and camera, and battery health. Erase and reinstall macOS last. If any must-check item fails, walk away; keyboard, ports, housing and the rest are optional extras.
Open System Settings > [your name] > iCloud > Find My Mac and confirm it is off and no previous owner's Apple Account remains. The safest method is to have the seller run Erase All Content and Settings in front of you; if Setup Assistant afterwards does not ask for the previous owner's password, the lock is gone. Never buy a Mac that still has Activation Lock.
Run profiles status -type enrollment in Terminal; both lines must say No. The more reliable test is to erase the Mac and connect to Wi-Fi during setup: a Remote Management screen means the Mac is company-supervised and can be locked or wiped remotely, so do not buy it.
On macOS Tahoe 26 or later, check System Settings > General > About > Parts & Service: if the display is listed, it was replaced (display records exist on M5 and newer Macs). On older Macs, confirm True Tone and auto-brightness work; a supported model with no True Tone option almost always has a non-genuine screen. Then look for pry marks around the bezel.
Use this site's dead pixel test to cycle full-screen red, green, blue, white and black and look for dots that never change. Then, in a dark room at 100% brightness, check the corners for backlight bleed; a faint, even glow at the edges is normal for LCD panels.
On macOS Tahoe 26 or later, open System Settings > General > About > Parts & Service. It lists every detected repair and labels each part as Genuine Apple, Used Apple, Unknown or Unverified. The menu only appears when a repair was detected, so no menu usually means no recorded repair.
Shut down and unplug everything except power. On Apple silicon, hold the power button until Options appears, then press Command-D. On Intel, press and hold D right after turning it on. Reference code ADP000 means no issues were found; any other code identifies a hardware fault.
No installation and no cost. xiaogua.org runs entirely in the browser: the dead pixel, camera, microphone, speaker, keyboard, trackpad and refresh-rate tests never upload any data. The guides are available in Chinese, English, Japanese, Spanish and Portuguese.