Testing · Buying Guide · Tips · 11 min read · October 8, 2026

How to Test Used Electronics Before You Buy: Complete Checklist

Trust but Verify

The seller says it "works great" — that means nothing. A laptop can "work great" with a battery that lasts 20 minutes, a keyboard with stuck keys, and a failing hard drive. Testing takes 5-10 minutes and can save you hundreds of dollars on a device that's about to fail.

Laptop Testing Checklist

Battery health (most important)

Battery replacement costs $50-$150. Check battery health before anything else:

• Windows: Open CMD, run powercfg /batteryreport, open the HTML report. Look at "Design Capacity" vs "Full Charge Capacity." Below 70% means the battery needs replacement soon
• Mac: Hold Option, click the Apple menu → System Information → Power. Check "Cycle Count" and "Condition." Over 800 cycles or "Service Recommended" means replacement needed

Screen defects

• Open a pure white image (search "white screen test") — check for dead pixels, bright spots, or yellowing
• Open a pure black image — check for backlight bleed (bright areas around edges)
• Move a window around the screen — check for ghosting or unresponsive areas on touchscreens

Keyboard and trackpad

• Open a text editor and type every key. Every single one. Sticky or non-responsive keys are common and expensive to fix on modern laptops
• Test the trackpad: click, right-click, scroll, multi-finger gestures

Storage health

SSDs have a finite write life. Check the drive's health:

• Windows: Download CrystalDiskInfo (free). It shows the drive's health status and SMART data. "Good" is good; "Caution" or "Bad" means walk away
• Mac: Open Disk Utility → select the drive → check SMART status. "Verified" is good; "Failing" is a hard no

Phone Testing Checklist

IMEI check (mandatory)

Before anything else, verify the phone isn't stolen or blacklisted. Get the IMEI (Settings → About Phone → IMEI) and check it at imei.info or your carrier's IMEI checker. A blacklisted phone is a paperweight.

Battery health

• iPhone: Settings → Battery → Battery Health. Below 80% means it needs a new battery
• Android: Dial *#*#4636#*#* on some phones, or install AccuBattery and charge/discharge once to get a capacity estimate

Screen and touch

• Check for screen burn-in: open a solid gray image and look for ghost images
• Test touch response in all four corners — edge dead zones are common after screen repairs
• Check for green lines or discoloration (OLED aging)

Sensors and features

Test: camera (front and rear), fingerprint reader, face unlock, speakers (both), microphone (record a voice memo and play it back), charging port (plug in and verify it charges), WiFi connection, Bluetooth pairing.

Desktop Testing Checklist

• Boot it up — listen for clicking or grinding sounds (HDD failure signs)
• Check all USB ports (plug something into each one)
• Verify RAM amount matches listing (Task Manager → Performance → Memory)
• Run a stress test (Prime95) for 5 minutes — if it crashes or overheats, the cooling is insufficient
• Check all video outputs work (HDMI, DisplayPort)

Red Flags: Walk Away

• Seller won't let you test: "It works, trust me" → don't trust them
• Factory reset right before sale: They may be hiding software issues, activation locks, or malware
• Mismatched serial numbers: Device serial doesn't match the box or paperwork = stolen or swapped parts
• Physical damage to the motherboard area: Dents near ports or screws can indicate internal damage
• Water damage indicators triggered: Check the SIM tray (phones) or bottom vents (laptops) for red/pink water indicators