Test a used laptop in ten minutes before you pay

Ten minutes with a used or refurbished laptop can reveal faults that would otherwise turn up after you have paid. Work through the screen, keyboard, touchpad, camera, microphone, speakers, ports and battery, in that order, with the laptop plugged in. The browser tests on this site need nothing installed, so they run on the seller's machine as easily as on yours.

Screen

1. Open the dead pixel test and start the full-screen test. Step through black, white, red, green, blue and grey. A dead pixel stays black on every colour, and a stuck pixel stays one colour. Look at the edges and corners as well as the middle.
2. Check for backlight bleed on the black step, in a dim room. Light leaking from the edges, or uneven bright patches, is backlight bleed. Some bleed is common on LCD panels, so judge how strong it is and whether it bothers you before you agree a price.
3. Check the resolution on the screen resolution page. It estimates the physical pixels as the screen width times the device pixel ratio. A laptop sold as 1920 × 1080 should read close to that, allowing for the browser's scaling. The figure is an estimate, so use it as a check against the listing rather than a measurement.
4. Measure the refresh rate with the refresh rate test, with the laptop plugged in. On battery, or in battery saver mode, a browser can draw fewer frames, so the reading can come out low. The test reports what the browser receives, not the rating printed on the panel.

Keyboard and touchpad

1. Open the keyboard test, click the box, and press every key, including the arrows, Enter, Backspace and the function row. Brightness and volume keys are handled by the system, so they may not reach the page. A silent brightness key is not necessarily broken, so test those by hand.
2. Hold several keys together. The most-held counter shows what the browser reads. If a combination fails, the keyboard may suffer from ghosting. Keyboard ghosting and rollover explains how to test that properly.
3. Test the touchpad with the mouse test. Click the left and right areas, scroll with two fingers, and try a double-click. A trackpad sends many wheel events for one gesture, so the wheel counts climb quickly. A touchpad may have no middle button, which is normal. A double-click fault means one press registered twice inside the window you chose, so watch that count.

Webcam, microphone and speakers

1. Start the webcam test. Check the live picture, its sharpness and the measured frame rate. A dark or grainy picture in good light can mean a dirty lens or a weak sensor. A black picture can mean a privacy shutter, or another app holding the camera.
2. Speak with the microphone test. Watch the level move as you talk, then record five seconds and play them back. The test reports silence if the input is dead. Record a short clip in another app as well, and listen for hiss or crackle.
3. Play left, right and both in the speaker test. Keep the volume low. Each side should play its chime, and a dead side points to the speaker or its connection. Most laptops have stereo speakers, so listen for a clear left and right.

Ports and battery

1. Plug in a USB device you know works, such as a mouse, and check that the laptop recognises it. Try every USB port, because a faulty port may show up on one side only.
2. Connect headphones to the audio jack and check the sound. If the laptop has a video port, connect an external display and look for a picture on it.
3. Check the charging port. Plug in the charger and check that the laptop shows it is charging. Wiggle the cable gently, because an intermittent charge can mean a loose port. Look inside the port for lint or bent pins before you blame the charger.
4. Read the battery report. On Windows, open a command prompt and run powercfg /batteryreport. It saves an HTML report that compares the design capacity with the full charge capacity. A full charge figure well below the design figure means the battery has worn. On a Mac, hold Option, click the Apple menu, choose System Information and open Power. It shows the cycle count and a condition, such as Normal.

These reports come from the operating system, and they are estimates. fixmint has no battery tool, so treat the report as one input. A battery that looks healthy on paper can still run down quickly under load.

Edge cases

• Refurbished units. Check the warranty terms and whether they cover the battery. A refurbished laptop can have a shorter warranty than a new one, so ask before you pay.
• Accounts and locks. Ask the seller to sign out of their accounts. Check that the laptop reaches its normal login screen, and does not ask for the seller's password or a management account.
• Heat and fan noise. Run the laptop for ten minutes or more before you judge its fan and temperature. A fan that is loud under load can be normal, or it can be dust, which is a cleaning job rather than a fault.
• Repairs. A dead pixel usually cannot be repaired. A stuck pixel sometimes recovers, but results vary. Factor that into the price.