How to check a used phone or laptop before you buy it

A second-hand phone or laptop can be a great deal — or a locked, water-damaged or worn-out problem that only shows up a week later. Most faults are easy to spot if you know where to look. Take this list with you and go through it on the device itself, before money changes hands.

Before you meet

• Ask for the bill and the box. The IMEI on the box should match the phone. A seller who has neither is not always a thief, but it is worth more questions.
• Get the IMEI (dial *#06# on the phone) and check it. In India, the government's Sanchar Saathi service tells you if a phone is blacklisted, a duplicate or already in use: send KYM <15-digit IMEI> by SMS to 14422, or use the Know Your Mobile app or the CEIR website. Elsewhere, ask your carrier or use your country's official blacklist check.
• Meet somewhere with Wi-Fi or good signal and bring a charger and earphones, so you can test charging and the headphone output.

Locks and accounts — check these first

This is the most important step. If the previous owner's account is still on the device, you may not be able to set it up as yours.

• iPhone and iPad: Find My must be turned off and the Apple Account removed. Then the seller should erase it. Set it up in front of them to be sure.
• Android: the seller should remove their Google account and factory reset it. Otherwise the phone will ask for their Google password after a reset.
• Laptop: make sure you can sign in and that there is no firmware or BIOS password. On a Mac, Find My Mac must be off and the Apple Account signed out.

The 15-minute phone check

1. Screen and touch

Open Screen Test on the phone and run the full-screen colours. On black, coloured dots are stuck pixels and glowing edges are backlight bleed. On white, black dots are dead pixels. On grey, look for faint shapes of the keyboard or status bar — that is burn-in, common on older OLED screens. Then run the touch grid and drag your finger over every square; any square that never fills is a dead zone.

2. Speakers, earpiece and microphone

Play the left and right check and the sweep in Speaker & Headphone Test at full volume and listen for buzzing or rattles. Make a short call to test the earpiece. Then record yourself in Microphone Test and play it back — muffled or crackly audio often means a damaged mic or water damage.

3. Cameras

Take photos with every rear lens and the front camera, in bright light and indoors. Look for blur that won't focus, haze, dark spots or a shaky preview. On a laptop, open Webcam Test to check the picture, real frame rate and lighting.

4. Battery

• iPhone: Settings → Battery → Battery Health. Below about 80% maximum capacity, the battery is due for replacement — factor that into the price.
• Android: some phones show battery health in Settings → Battery or in the maker's support app; many don't. Watch how fast the percentage drops while you test, and whether the phone gets hot doing simple things.

5. Charging port, buttons and SIM

Plug in your charger and gently wiggle the cable — charging should not keep cutting in and out. Press every button: power, volume, mute. Put in your SIM card and make a call, so you know the phone isn't locked to another network.

6. Signs of water damage

Look into the charging port with a torch for green or white corrosion on the pins. Many phones also have a small liquid indicator sticker, often visible in the SIM slot, that turns red or pink after contact with water.

7. Speed and heat

Run Device Performance. It shows how long real jobs — resizing photos, merging a PDF, opening a big spreadsheet — take on that device, in plain words. If you have a few minutes more, its heat test shows whether the phone slows down badly as it warms up.

Extra checks for a laptop

1. Every key. Open Keyboard Test and press every key once. Each one lights up when it works. A key marked as "typed twice" has a worn or dirty switch.
2. Touchpad and mouse buttons. In Mouse Test, click every button and run the hold test — if a drag keeps letting go, the button is worn.
3. Battery health on Windows. Open Command Prompt, type powercfg /batteryreport and open the battery-report.html file it saves in your user folder. Compare Full Charge Capacity with Design Capacity — the lower it is, the more the battery has worn.
4. Battery health on a Mac. Hold Option, click the Apple menu and choose System Information, then Power. Check the cycle count — most recent MacBooks are rated for 1,000 cycles.
5. Battery vs plugged in. Run Device Performance once on battery and once plugged in. A huge drop on battery can point to a tired battery or a power setting.
6. Ports, hinge and screen. Try each USB port, open and close the lid a few times (no creaking or wobble), and run the Screen Test colours.

Quick checklist