How to check a used laptop before you buy it
The short answer
Check a used laptop on the laptop itself, with the seller there, before you pay. Run a dead pixel test, press every key, test the trackpad clicks, turn on the camera and record from the mic, play each speaker, plug something into every port, read the battery's full charge capacity against its design capacity, and make sure the seller has signed out of their Apple or Microsoft account. It takes about fifteen minutes.
A used laptop hides its faults well. The seller has had months to get used to the key that needs pressing twice, and none of it shows in the photos. Fifteen minutes on the laptop itself, before any money changes hands, finds most of what goes wrong.
Do every check on the laptop you are buying. Open the browser on that machine, not on your phone. The laptop check walks you through each test below in order, keeps your marks while you open each test in another tab, and prints a one-page record at the end.
Bring three things
A USB stick or a phone with its cable, wired earphones, and the laptop’s charger if the seller has not got it out. Without something to plug in, you cannot tell a dead port from a working one, and ports are a common fault on laptops that have been carried around for years.
The screen
Turn the brightness up, go fullscreen with a dead pixel test, and step through every colour. A dot that stays black on every colour is a dead pixel; one that stays red, green or blue is stuck. On the black screen, look at the edges for light leaking in, which is backlight bleed. The guide to checking a screen before the return window closes explains what is normal and what is a fault.
Look at the screen from the side, too. Lines, a yellow patch or a pressure mark from the keyboard (on a laptop that was closed on something) all show best at an angle.
The keyboard and trackpad
Press every key in a keyboard test. Every key you press should light up once. A key that stays dark is not reaching the computer; a key that lights twice from one press is chattering, and the guide to keys not working or typing twice explains each fault. Laptop keyboards are expensive to replace because on many models the keyboard is riveted to the top case.
Then click the trackpad: left, right, and a minute of single clicks in the mouse test. A button that sends a double click from one press is wearing out.
Camera, mic and speakers
Turn on the camera in the webcam test and check the picture is clear and the frame rate holds. Record a sentence in the mic test and play it back; it tells you if the mic is quiet, noisy or distorted. Play each side in the speaker test and listen for a dead side or a rattle at high volume.
Ports and charging
Plug the USB stick or phone into every port and check the laptop sees it. Plug the earphones into the audio jack and play something. Plug in the charger and watch for the charging light or icon, then wiggle the plug gently: a charge that comes and goes means a worn socket.
The battery
This is the check most buyers skip and the one that costs most later. A browser can read the battery’s current charge but not its health, so use the laptop’s own report. On Windows, open Command Prompt and run powercfg /batteryreport, then open the file it names and compare Full charge capacity with Design capacity. On a Mac, hold Option, open the Apple menu, choose System Information, then Power. How to check laptop battery health goes through every system and what the numbers mean.
Locks and accounts
A laptop still tied to the seller can be unusable. Ask them to sign out of their Microsoft account or Apple ID and reset the laptop in front of you. On a Mac with Apple silicon or a T2 chip, Find My must be off: otherwise Activation Lock asks for the seller’s Apple ID password after the Mac is erased. On any laptop, restart it and press the setup key (often F2, Del or Esc) to see whether the firmware asks for a password.
The body
Open and close the lid; it should hold any angle. Look for cracks around the hinges, missing screws and a trackpad that sits higher at one edge, which can mean a swollen battery underneath. A swollen battery is a safety problem, not a bargaining point.
What fifteen minutes cannot tell you
No browser test sees the health of the hard drive or SSD, the temperatures under load, or water damage inside the case. For the disk, the maker’s diagnostics (Dell SupportAssist, HP PC Hardware Diagnostics, Lenovo Vantage) can run a check. For everything else, a return window or a short warranty is the protection. Keep the printed result from the laptop check with the receipt: it records what worked on the day you bought it.
- Laptop
- Buying
