Display Test HDR brightness test
HDR peak brightness test
Find out how bright small HDR highlights get on your screen, and how much it dims large bright areas. You click the first box where a small square disappears into its frame – no tools or knowledge needed.
About 2 minutes · Free, no sign-up · Results stay on this device.
Detected automatically
How the test works
HDR (high dynamic range) lets a screen show highlights brighter than normal white. You see a row of 12 small boxes. Each frame is driven far brighter than any screen can show, so it sits at your screen’s maximum. The square inside has an exact brightness from 1× to 16× normal (SDR) white – the white of an ordinary web page.
Click the first box where the square disappears into its frame; a finer row then appears for a precise pick. If you see the square in every box, your screen most likely tone maps – it squeezes bright tones instead of cutting them off. The second part uses bigger boxes (about 10% of the screen is bright instead of 2%) to show how much your screen dims large bright areas. Nothing flashes.
What you need
- Chrome or Edge on Windows or Mac, not Safari or Firefox.
- HDR turned on. Windows: Win + Alt + B, or Settings → System → Display → Use HDR. Mac: XDR displays switch to HDR on their own; for other HDR monitors, turn on High Dynamic Range in System Settings → Displays. With HDR off, the result explains how to turn it on.
- Your usual HDR picture mode – the result describes that mode.
Reading your result: from × to nits
The result is a multiple of normal white, for example 4.5×. On Windows, enter your SDR content brightness slider value (Settings → System → Display → HDR). Normal white in nits is 80 + 4 × the slider value: at 30 that is 200 nits, so 4.5× is about 900 nits. On a Mac the result stays a multiple, because normal white follows your brightness setting.
- Small highlights: under 300 nits is entry-level HDR, 300–500 good, 500–800 very good, 800–1200 excellent, above 1200 outstanding. An HDR400 or HDR1000 label names the rated peak brightness in nits – useful for a rough comparison.
- Large bright areas: under 15% dimmer than small highlights means the screen keeps its brightness, 15–45% is typical for OLED, above 45% is strong brightness limiting.
Browsers cannot read nits, so this is a visual estimate of where your screen reaches its maximum, relative to SDR white. If you own a colorimeter (a screen-measuring device), you can add its reading to the report.
How to get more from HDR
- Square in every box: on a TV, choose HGIG (it leaves tone mapping to the game) or turn off dynamic tone mapping. On a monitor, try a “Peak 1000” or “True Black” HDR mode.
- Dim highlights: lower the Windows SDR content brightness slider to leave more room above normal white.
- Calibration: in the free Windows HDR Calibration app for Windows 11 (Microsoft Store), set maximum brightness to the nits estimated here.
- Strong dimming (ABL): “True Black 400” is steadier for desktop work; “Peak 1000” gives brighter highlights for films and games.
Not every screen has these modes, and names vary. See also the black level test and the colour gamut test.
Questions
How do I turn on HDR in Windows?
Press Win + Alt + B, or open Settings → System → Display and switch on Use HDR. This works only if your screen supports HDR. If the HDR card on this page still says Off, reload the page.
Can a browser measure my screen’s nits?
No. Browsers cannot read brightness, so this test shows exact brightness steps and you judge where they stop. On Windows, the SDR content brightness slider turns that into an estimate in nits; for a measured value you need a colorimeter.
Why can I see the square in every box?
Most likely your screen tone maps: instead of cutting off at its maximum, it squeezes bright tones together so they stay visible. With a very low SDR content brightness setting, a very bright screen may also simply reach more than 16× normal white. For games, HGIG or a mode without dynamic tone mapping lets the game’s own HDR settings work as designed.
What is ABL on an OLED screen?
ABL (auto brightness limiter) lowers brightness when a large part of the screen is bright, to limit power and heat. It is normal for OLED, and the Large bright areas step shows how strong it is on your screen.
Does the HDR test work in Safari or Firefox?
Not at the moment. They show this test in SDR, so the squares cannot get brighter than normal white. Use Chrome or Edge with HDR turned on.
Does the HDR test work on a phone?
Usually not. Most phone browsers don’t show HDR on web pages, so the test skips the HDR steps and says why. To test an HDR monitor or TV, use Chrome or Edge on a Windows PC or Mac.
Check everything in 5 minutes
The full Display Test covers HDR brightness, black level, gradients, colours, motion, dead pixels and burn-in – one simple step at a time, with a report you can save as PDF.
More single tests
- Black levelTrue black and the darkest shadow detail.
- GradientsStripes in smooth colour ramps – 8-bit or 10-bit.
- ColoursStandard sRGB, Display-P3 or beyond.
- Refresh rateYour Hz right away, plus motion clarity.
- Dead pixelsDark or stuck dots on full-screen colours.
- Burn-inFaint shapes left by static images on OLED.
- UniformityPatches, darker edges and backlight bleed.
Every pattern is drawn live at your display's native resolution with exact brightness values – no compressed video. · PeakNits home · Music visualizer · Privacy · Statistics settings