Cleaning a monitor
A bright, even screen makes dust, smudges and fingerprints obvious. Check first, power the display off, then wipe with a dry microfibre cloth.
Contrast test
Run a full contrast test straight from your browser. Everything happens on your own device — no upload, no account, nothing installed. It works the same on a phone, a tablet, a laptop screen or a 4K desktop monitor, and it takes under a minute.
F Tap anywhere to go fullscreen
Click the screen or press F. Press Esc to exit. · 100% free. No sign-up. Works offline.
This pattern is two staircases of grey, one climbing from black and one falling from white, each in equal steps. On a display with a well-behaved response you can count every step at both ends. Where the steps merge, your display is clipping — throwing away detail that is present in the signal.
Losing steps at the dark end is black crush, and it means shadow detail vanishes in films and games. Losing them at the bright end is white clipping, where highlights turn into flat white and skies lose their gradation. Both are usually caused by settings rather than by the panel.
Before blaming the display, check that your graphics driver is sending full RGB rather than limited. A limited-range signal shown on a full-range display crushes both ends of this pattern at once, which is the single most common cause of the effect.
What this checks
- How many steps are distinguishable at the dark end — black crush
- How many are distinguishable at the bright end — white clipping
- Whether the steps rise evenly or bunch up in the middle
- Colour tinting that appears in the near-black steps, common on cheaper panels
How to use it
Open the screen
Click or tap the preview panel. Your browser switches to true fullscreen and hides every menu bar and toolbar.
Adjust it
Use the brightness slider and the colour temperature control to get exactly the light you need. Your settings are remembered on this device.
Use it
Clean, test, light or focus. Move the mouse or tap once to bring the controls back at any time.
Exit
Press Esc, or tap the close button in the corner, to return to this page.
What people use it for
Finding dead pixels
A dead pixel stays black on white; a stuck pixel glows red, green or blue on black. Cycling solid colours is still the fastest way to find both.
Video call lighting
A white or warm-white screen beside your face fills in shadows far better than a ceiling light, and costs nothing.
Photography and video
A tablet running a solid colour makes a usable fill light, catch light or small backdrop for product shots.
Tracing and drawing
A tablet on maximum brightness under thin paper works as an improvised light table for tracing and flip-book animation.
Focus and presenting
A blank screen hides your desktop during a presentation and removes visual clutter while you concentrate.
Frequently asked questions
Is the contrast test really free?
Yes. Every tool on this site is free, with no account, no trial and no paid tier. You do not need to give us an email address.
Does it work on a phone or tablet?
Yes. The whole site is built mobile-first and works in Safari on iPhone and iPad, Chrome on Android, and every modern desktop browser. On iOS, fullscreen uses a full-viewport mode because Safari restricts the fullscreen API.
Does it work offline?
Yes. After your first visit the page is cached on your device, so you can open it again with no internet connection at all.
Will this damage my screen?
No. Displaying a solid colour is exactly what your screen does all day. The one caution is OLED: leaving a static bright image on an OLED panel for hours can cause temporary image retention, which is why we include an optional burn-in protection mode.
Do you collect my data?
We do not ask for a name, an email or an account, and no image ever leaves your device — every tool renders locally in your browser.
I cannot see the darkest steps at all.
First check whether your graphics output is set to limited RGB — switching it to full fixes this more often than anything else. After that, lower the display's contrast setting, since a high contrast control clips the top of the range and a high black-level control crushes the bottom.
Does this measure contrast ratio?
No. Contrast ratio is a measured quantity that needs a light meter. This pattern shows something more practically useful: whether your display is actually reproducing the range it is being sent, or discarding the ends of it.
Should I test in a dark room?
Test in the room you actually work in. Shadow detail visible in a pitch black room can be entirely invisible in daylight, so calibrating for conditions you never use is not much help.
Guides
Monitor Calibration Guide: What You Can Do by EyeHow far you can get calibrating a display by eye with test patterns, where visual calibration stops being reliable, and when a colorimeter is worth buying.IPS vs VA vs TN vs OLED: Which Panel Type Should You BuyA practical comparison of the four panel technologies — contrast, viewing angles, speed, burn-in risk — and which one fits which kind of use.How to Reduce Eye Strain From Screens (What Actually Helps)Evidence-led adjustments for digital eye strain: brightness, contrast, distance and blink rate — and an honest look at blue light filters.