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RetinaDesk

Tool

Full-screen monitor test

Check a new display the way we check the ones we review. There are 11 full-screen tests for dead pixels, bleed, banding, gamma, sharpness, colour and motion. Mark what you see and it becomes a report you can keep, or paste into a return request while you can still send the monitor back.

  • ←→ between tests
  • Space next pattern
  • Esc leave any time

Now showing Gradients & banding

Detected live

This display, as your browser sees it

Drag this window to another monitor and the readings follow it.

Looks like
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points macOS lays out

Rendered at
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device pixels

Colour
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widest gamut reported

Refresh
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Pick the panel’s resolution and we’ll tell you whether macOS is drawing it pixel for pixel.

Pick a test, or run them all.

Each card is playing the real pattern. Open one to go full screen. The controls get out of the way when you stop moving the mouse, so nothing sits on top of what you’re judging.

0 of 11 checked

Before you start

  • Warm it up. Leave the monitor on for 20 minutes. Uniformity and colour settle as the backlight warms.
  • Wipe the glass. Dust looks exactly like a dead pixel. A microfibre cloth saves a false alarm.
  • Native resolution. Pick the resolution that matches the panel, or the sharpness tests are testing macOS scaling instead.
  • True Tone & Night Shift off. Both tint the whole screen. Turn them off in System Settings › Displays while you test.
  • Dim the room. Bleed and near-black steps only show up with the lights low and no glare on the screen.

Your report

No results yet

Run the inspection and your verdicts collect here. They stay in this browser. Nothing is uploaded.

    Tool

    Mac PPI calculator

    Moiré in the scaling test? See why the panel’s density decides how macOS scales it.

    Open tool

    Tool

    Cable bandwidth calculator

    Stuck at 60 Hz or 30 Hz? Check whether your cable can carry the refresh rate you paid for.

    Open tool

    Reviews

    Every 5K and 6K monitor we’ve tested

    Sending one back? These are the Retina-density panels we would buy instead.

    Browse monitors

    How to test a new monitor before the return window closes

    Most retailers give you 14 to 30 days, and panel defects are easiest to argue while the box is still in the hallway. Warm the monitor up, set it to its native resolution, and run the inspection once in daylight and once with the lights low. Dead pixels and coating grain show up best in daylight. Backlight bleed and crushed shadows only appear in the dark.

    Flag anything that bothers you, even if you are not sure it counts as a fault. The report records what you saw and where, and it is much easier to decide on a return with notes in front of you than from memory a week later.

    What makes this test different on a Mac

    Most online monitor tests draw their patterns in CSS pixels. On a Retina Mac one CSS pixel is four physical pixels, so a "1 pixel" checkerboard is really a 2 × 2 block, and the test can’t tell a sharp panel from a soft one. Every pattern here is drawn in device pixels. A stripe one pixel wide is one physical row on the panel, which is what the gamma and scaling tests need to work at all.

    That also lets the tool show something specific to macOS. When the resolution you choose doesn’t double to the panel’s native grid, macOS resamples the whole desktop. Tell the tool your panel’s native resolution and it shows how far the desktop is being scaled, and the Retina & scaling test lets you see the effect.

    Reading the results honestly

    • Some IPS glow is normal. If the glow moves as you move your head, it is the panel type, not a defect.
    • Banding at 256 steps is partly the signal. Web pages are 8-bit, so a very wide screen shows faint steps even on a perfect panel. Judge whether the steps are even and neutral, not whether you can see them.
    • Gamma depends on settings. Picture modes, “dynamic contrast” and colour presets all move the gamma bar. Reset the monitor before you judge the panel.
    • Browsers throttle. Low Power Mode, a busy tab or Safari’s frame cap can all make the motion test read low. Close other tabs and try Chrome before you blame the display.

    Frequently asked questions

    How do I check a new monitor for dead pixels?

    Open the dead and stuck pixel test full screen and step through the solid colours with the space bar. Look at the screen in sections from about 30 cm away. When you find a dot that does not match, click it. Then check the same spot on the other colours and click it again each time you see it. The tool combines the clicks into one marker and tells you whether it is a dead, stuck or hot pixel. Wipe the screen first, because dust looks exactly like a dead pixel.

    What is the difference between a dead, a stuck and a hot pixel?

    A dead pixel stays dark. You see it as a black dot on white and on bright colours. A stuck pixel has one or more subpixels stuck on, so it shows as a red, green or blue dot on black. A hot pixel is lit on every colour, including black. Stuck pixels sometimes recover with the stuck pixel exerciser. Dead and hot pixels almost never do.

    How many dead pixels are acceptable before I return a monitor?

    It depends on the manufacturer. Most pixel policies follow the ISO 9241-307 classes, which allow a small number of defects before a panel counts as faulty, and bright pixels are usually treated more strictly than dark ones. A few premium lines promise zero bright pixels. Check the policy for your model, and test inside the return window, because a store return is usually far easier than a warranty claim. The report from this tool gives the location and type of every defect you marked, ready to paste into a claim.

    Is it backlight bleed or IPS glow?

    Move your head. IPS glow is a soft, often silvery or amber haze in the corners that changes as you change your viewing angle, and it fades as you sit further back. Backlight bleed is light leaking around the edge of the panel. It stays in the same place and keeps the same shape wherever you look from. Some glow is normal for every IPS panel. Bright, fixed bleed you can see during normal dark scenes is a defect.

    Why does the checkerboard ripple or show moiré on my Mac?

    Because macOS is resampling the desktop. On a Mac you choose a "looks like" resolution, and macOS draws it at twice that size. If that doubled size is not the panel's native resolution, as with "looks like 2560 × 1440" on a 4K monitor, every frame is scaled on its way to the panel. A pattern of single physical pixels cannot survive that, so it turns into ripples and grey mush. It is the same softness you see in small text, which is why 5K at 27 inches and 6K at 32 inches are the sizes that suit macOS best.

    Why does the motion test say 60 Hz on my 120 Hz display?

    Check three things. First, the Mac: System Settings › Displays › Refresh rate must be set to the higher rate. Second, the cable and port: many USB-C and HDMI links cannot carry high refresh rates at 4K or above, and our cable bandwidth calculator shows which ones can. Third, the browser: Safari has held web pages to 60 frames per second on ProMotion displays unless a developer setting is changed, so run the motion test in Chrome to see the full rate.

    Is the stuck pixel exerciser safe?

    For the monitor, yes. It only switches pixels between colours, which is what they do all day anyway. It does flash rapidly, so do not use it if you are sensitive to flashing light. The tool asks you to confirm before it starts. Run it for 10 to 20 minutes over the stuck pixel. It can free a stuck subpixel but it cannot repair a dead one.

    Does anything get uploaded?

    No. Every test runs in your browser. Your verdicts, notes and marked pixels are saved in this browser only, so you can close the tab and come back to them. The report is text that you copy or download yourself.