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Checking a Used Laptop Before You Buy

By Jayadeep · Updated August 2026 · About 10 minutes

Eight checks you can run on the seller's machine, in front of the seller, before any money changes hands.

A used laptop is the hardest secondhand purchase to inspect, because almost every expensive failure is invisible when the lid is closed and the machine is off. A cracked hinge shows itself immediately; a dying battery, a dead patch on the trackpad, a keyboard with three unresponsive keys and a webcam that no longer initialises do not. Sellers are frequently not hiding these — plenty of people genuinely do not know, because they used an external monitor and keyboard for two years.

The economics are what make this worth ten minutes. Most of the faults below are repairable, but the repair costs are a large fraction of what you are paying for a secondhand machine: a battery replacement, a keyboard assembly, a screen. Finding one before you pay converts it into a negotiating position. Finding it afterwards makes it your problem entirely, because private secondhand sales rarely carry any return rights.

Run these in order. The sequence is deliberate — it starts with the checks that are cheapest to perform and most expensive to get wrong, and it front-loads the display, because a panel fault is the single most common reason to walk away. Every step below runs in the seller's browser with nothing installed and nothing uploaded, so there is no reason for a seller to object.

The checklist

Tick each step as you go — the order matters, because the early checks are the ones most likely to end the negotiation. Your place is saved in this browser, so you can pause if the seller needs a moment.

0 of 8 done

  1. Cycle white, black, red, green and blue at full screen. Look for dots that stay fixed as the colour changes, and for bright clouding along the panel edges on black.

    Open the Dead Pixel / Screen →

    Pass: A clean panel on every colour, with no fixed dots and no obvious light leak on black.

    Fail: Fixed dark or bright dots, or heavy backlight bleed visible on the black field.

    If it fails: Dead pixel vs stuck pixel — Work out whether it is dead or stuck, and whether it is worth negotiating on.

  2. Read the reported resolution and pixel ratio, and compare them with the specification for that model.

    Open the Screen Resolution & Info →

    Pass: Reported resolution matches the model's advertised panel resolution.

    Fail: A lower resolution than advertised, which can mean a replaced panel.

    If it fails: Find your screen resolution — Confirm what your screen is actually reporting and why it might differ.

  3. Work across the whole keyboard row by row, including modifiers and the function row. Watch each key light up as you press it.

    Open the Keyboard Test →

    Pass: Every key registers exactly once, first time.

    Fail: A key that never registers, or one that registers twice from a single press.

    If it fails: Some keyboard keys not working — Separate a dead switch from a driver or layout problem.

  4. Move the pointer across the full width of the screen, then test left, right and middle click and scrolling.

    Open the Mouse & CPS Test →

    Pass: Smooth tracking with no jumps, and every button registering a single clean click.

    Fail: Pointer jumps, dead zones, or a single click registering twice.

    If it fails: How to fix a mouse that double-clicks on its own — Diagnose a double-click fault, which is mechanical and progressive.

  5. Start the preview and confirm a live picture appears. Check the image is not heavily blurred or discoloured.

    Open the Webcam Test →

    Pass: A clear live picture within a second or two of granting permission.

    Fail: A black frame, no device listed, or a badly degraded image.

    If it fails: Webcam not detected on Windows — Rule out a permission or device-selection problem before blaming the hardware.

  6. Watch the level meter while speaking at normal volume, then record a few seconds and play it back.

    Open the Microphone Test →

    Pass: The meter responds to your voice and the playback is clear and intelligible.

    Fail: No meter movement, or playback that is inaudible, distorted or full of noise.

    If it fails: Microphone not working on Windows 11 — Check whether it is the hardware or a Windows input setting.

  7. Play the test tone and listen to each channel in turn, with the volume at a moderate level.

    Open the Speaker Test →

    Pass: Both channels produce clean sound at similar volume.

    Fail: One silent channel, an obvious volume imbalance, or crackling and distortion.

    If it fails: Speakers crackling or popping — Identify whether it is the driver, the amplifier or a loose connection.

  8. Unplug the charger first, then read the level and the estimated time remaining. Watch it for a minute.

    Open the Battery Test →

    Pass: A plausible level that falls slowly, with a sensible time estimate.

    Fail: A level that collapses quickly once unplugged, or a machine that shuts down without the charger.

    If it fails: How to check laptop battery health — Understand what the reading means and how to check cycle count in the OS.

More tests worth running here

Not essential to the checklist above, but relevant to this situation and quick to add.

Typing Speed TestTouchscreen TestHeadphone TestRefresh Rate Test

Frequently Asked Questions

How long does this checklist take?

About ten minutes if nothing is wrong, and it is worth doing all eight steps even when the first few pass cleanly. The battery step is the one people skip because it is last and requires unplugging the charger — it is also the most expensive fault to inherit, so do not skip it.

Will the seller mind me running these tests?

Most will not, because everything here runs in a browser tab with nothing installed, nothing downloaded and nothing uploaded. It is reasonable to explain that up front. A seller who refuses any inspection of a machine they are asking you to pay for is itself useful information.

What if the laptop has no internet where I am meeting?

Load each test page in a browser tab before you set out and leave the tabs open. The tests run entirely in the page once loaded, so they continue to work without a connection. Tethering to your phone also works.

The screen has one dead pixel. Should I walk away?

Not necessarily — a single dead pixel on a used machine is common and would not qualify for replacement under most manufacturers' policies even when new. It is a reasonable point to negotiate on rather than a reason to abandon the purchase. Clusters of dead pixels, or a large area of discolouration, are a different matter.

Does a browser battery reading tell me the battery's real health?

No, and it is important to be clear about that. The browser reports the current charge level and charging status, not the battery's maximum capacity relative to when it was new. For true health you want the cycle count and design-capacity figures from the operating system. The browser reading is a fast sanity check, not a substitute.

Is my progress on this checklist stored anywhere?

It is stored in your own browser using localStorage, so you can close the tab and pick up where you left off. It never leaves your device and there is no account, no sync and no server involved. Clearing your browser data clears it.

Other checkups

Every test in this checklist runs in the browser on the machine you are inspecting, so a seller can watch exactly what you are doing. Nothing is installed and nothing is uploaded. See how we validate these tests.

Found an error on this page, or a result that does not match your hardware? Tell us and we will correct it.