How to Test a Used Phone Before Buying
Last updated: August 2026
Why test before buying?
Buying a used phone saves money, but hardware defects can be expensive to fix. A quick browser-based diagnostic check can reveal screen issues, camera problems, sensor failures, and more — before you hand over any money.
What you need
- The used phone you are considering
- A modern web browser (Chrome or Safari)
- 5–10 minutes
Checklist
1. Screen test
Open the Screen Test and cycle through all colors. Look for dead pixels (black dots), stuck pixels (colored dots), and uneven backlighting. Check edges and corners carefully.
2. Touch screen test
Run the Touch Screen Test to check for dead zones (areas that do not register touch), ghost touch (phantom inputs), and overall accuracy.
3. Camera test
Use the Camera Test to verify both front and rear cameras work. Check resolution and confirm the camera can capture a snapshot.
4. Microphone test
Run the Microphone Test to verify the microphone picks up audio and input levels are reasonable.
5. Speaker test
Use the Speaker Test to confirm audio output works on both left and right channels.
6. Battery check
Run the Battery Test to read battery level, charging state, and health heuristic. Degraded battery health may indicate heavy prior usage.
7. GPS test
Use the GPS Test to verify location services work and check accuracy. Poor GPS may indicate a hardware issue.
8. Motion sensors
Run the Motion Sensor Test to check accelerometer and gyroscope. These sensors are used for screen rotation and gaming.
Run all tests at once
The health suite runs all supported tests in sequence and produces a combined report with a health score.
What this cannot test
Browser-based tests cannot check: physical damage (cracks, dents), water damage, SIM tray functionality, charging port condition, or cellular signal strength. For those, you need a physical inspection.