HDR Display Test: Check HDR Support on Your Monitor
HDR Display Test. Click Start HDR Test to run this HDR display test and compare bright highlights and deep shadows against an SDR version. The color banding test tool is free and runs entirely client-side, so nothing about your display is ever uploaded.
Interactive Tool
Filled in from your browser (dynamic-range: high). Change it if you know better.
What was enabled in your operating-system display settings?
The widest color-gamut media query your browser matches.
Screen color depth reported by the browser.
The VESA badge on your monitor's spec sheet, if any.
Comparison pattern you are viewing.
This HDR display test displays a bright-highlight-and-deep-shadow pattern next to an SDR comparison so you can judge whether high dynamic range is actually rendering on your screen, not just switched on somewhere in settings. Click Start HDR Test and compare the two fields — real HDR should show more separation between the near-black shadow detail and the bright highlight than the SDR version does; if the two look identical, HDR is likely capable but disabled, so check the HDR Support Checker to confirm what your browser can detect.
Bought a new monitor with an HDR badge and want proof it delivers? This HDR display test reads what your browser and system report, then walks you through test patterns that expose banding, halos and color shifts, so you learn the real HDR performance of your screen: how much contrast it holds, how far beyond sRGB its gamut coverage reaches, and whether the badge means anything.
How the HDR Display Test Checks Your Screen
The HDR display test runs in three layers. First it asks the browser two questions through CSS media features: does this display report HDR, and does it report a wide gamut? Then it shows comparison patterns you judge by eye. Finally it points you to the operating system, which decides whether HDR is actually switched on. Run the monitor contrast ratio test online for a few seconds under normal room lighting for the most reliable result.
- Drag the browser window onto the display you want to check.
- Read the HDR support and gamut results the page shows.
- Cycle through the patterns and note what you see.
- Confirm HDR status in your OS before trusting a "not detected" result.
Treat it as a quick dynamic range test of your setup, the free first stop before a full HDR detection tool or a meter. A "yes" on HDR capability tells you the pipeline is open, not how good the picture is.
What HDR Detection Can and Can't Confirm
Browser-side checking relies on the dynamic-range: high media query. A match means the browser, GPU and OS agree the signal path can carry HDR; it does not prove HDR is active or measure light output. Browser support also varies, so a Chromium-based browser and Safari may disagree on the same machine. An HDR test page can confirm the signal path, while peak output, gamut coverage and local-dimming quality need a colorimeter and dedicated test signals.
Reading the Gradient, Halo and Blooming Patterns
The SDR patterns use ordinary sRGB colors, so they compare behavior rather than measure HDR. Look for visible steps in the gradient (banding), a gray halo around bright shapes on black, and blooming where a small white dot spreads into a glow. Keep the same room lighting for every pattern so your notes stay comparable.
High Dynamic Range in Numbers: Brightness, Contrast and Color
High dynamic range combines three things standard dynamic range cannot: bright highlights well above normal white, deep blacks in the same frame, and more saturated colors. When all three line up, shadows keep their detail while a sunlit window still glows, and image quality jumps in a way you notice immediately. Run the free monitor color temperature test for a few seconds under normal room lighting for the most reliable result.
Peak Brightness, Black Level and Contrast in Stops
Two measurements set the size of the range: peak brightness (the brightest highlight, in nits) and black level (how dark black gets). Their ratio is the contrast, and photographers count it in stops, where each stop doubles the light:
$$\text{Contrast} = \frac{L_{peak}}{L_{black}} \qquad \text{Stops} = \log_{2}\left(\frac{L_{peak}}{L_{black}}\right)$$Take a Mini LED display that hits 640-nit peak brightness with a 0.045-nit black level. Its contrast is \(640 \div 0.045 \approx 14{,}222{:}1\), or about 13.8 stops. A typical IPS office display with a 320-nit peak and a 0.29-nit black manages only 1,103:1, about 10.1 stops. That 3.7-stop gap is roughly 13 times more contrast, and it is the difference you see in a dark scene.
Wide Color Gamut and Color Depth
HDR video is mastered in a wide color gamut: DCI-P3 today, inside the larger Rec.2020 color space. A display limited to sRGB clips those colors. Color depth matters too: 10-bit gives 1,024 levels per channel against 256 for 8-bit, which keeps a wide brightness range free of steps.
HDR Support Across HDR10, Dolby Vision and HLG
Four HDR formats cover almost everything you will play:
- HDR10
- The open baseline: 10-bit, PQ-encoded, with static metadata for the whole title.
- HDR10+
- Adds dynamic metadata, so brightness mapping changes scene by scene.
- Dolby Vision
- Dynamic metadata and up to 12-bit signals, common on a TV and on Netflix.
- HLG
- Hybrid Log-Gamma for broadcast, one signal for SDR and HDR sets.
Streaming HDR in a browser, on Netflix or YouTube, also needs hardware decoding on your graphics chip. Most services offer both Dolby Vision and HDR10.
The Perceptual Quantizer and Tone Mapping
HDR10 encodes light with the perceptual quantizer (PQ curve, SMPTE ST 2084), an EOTF that maps code values to absolute output from 0 to 10,000 nits. Unlike SDR gamma, it spends more codes on darker tones. For the example display, its 640-nit peak sits at about 70% of the signal, code 719 of 1,023. Anything mastered brighter must be squeezed by tone mapping; good mapping keeps highlight detail instead of clipping it white. The browser check cannot see the curve itself, but weak mapping shows up in the patterns as bright shapes flattening into plain white or as visible steps in the ramp.
HDR Testing a New Monitor Before Its Return Window Closes
A colorist working from home has a 27-inch Mini LED monitor sold as DisplayHDR 600, and the 30-day return window ends on Friday. The question is simple: keep it for grading, or send it back? The answer turned out to be keep it, but only with local dimming on, and the reason is in the numbers.
The first run of the check reports no HDR at all. That looks alarming until the Windows display page shows Use HDR switched off; after turning it on, the browser reports a high dynamic range and a P3-class gamut. Next come the patterns: on the bright-dot-on-black screen a faint ring appears around the dot, which is the dimming zones at work.
The spec sheet lists 612 nits peak and 0.071 nits black with local dimming on High. Dividing the two:
- 612 ÷ 0.071 = 8,620:1 contrast
- log2(8,620) = 13.07 stops
Cross-checking against VESA's DisplayHDR limits: the 600 tier allows a black level up to 0.1 nits, so 0.071 passes; the 1000 tier allows 0.05, so it would not. The sensitivity rerun is where it gets interesting. The same spec sheet lists a dimming-off black of 0.52 nits:
| Local dimming | Black (nits) | Contrast | Stops |
|---|---|---|---|
| High | 0.071 | 8,620:1 | 13.07 |
| Off | 0.52 | 1,177:1 | 10.20 |
Almost 3 stops vanish, and 0.52 nits is above even the DisplayHDR 400 limit of 0.4. The badge describes the monitor in one setting, not every setting. That is the caveat most buyers miss: a certified display can drop below the entry tier the moment someone turns dimming off to get rid of the halo.
My judgement: black level is the input to watch here, not peak brightness. Raising peak from 612 to 700 nits would add only 0.19 of a stop, while the dimming toggle moves the result by 2.87 stops. So the plan is dimming on High for grading HDR footage, Medium for the desktop, and a repeat of the whole check after the next firmware update, since dimming algorithms often change.
DisplayHDR Certification and Real HDR Performance
VESA's DisplayHDR certification sets minimums for brightness, blacks, gamut and bit depth, and the number in each name is the required peak output. DisplayHDR 400 is the entry tier, DisplayHDR 600 is where HDR performance becomes clearly visible, and DisplayHDR 1000 adds strong local dimming. True Black tiers cover OLED, which trades peak output for near-zero black. Our 640-nit example clears the 600 tier but falls short of 1,000.
Spotting Fake HDR on Budget Monitors
A display that accepts an HDR10 signal can still be fake HDR: an edge-lit LCD monitor with a 350-nit peak and no dimming zones raises its whole backlight for one highlight, so blacks look washed out and the image can look worse than SDR.
HDR Capability by Panel Type
Display technology decides most of the result, and it predicts what the bright-dot-on-black pattern in this check will show you. Light control matters more than any spec-sheet number:
| Display tech | How it controls light | What the bright-dot pattern shows | HDR verdict |
|---|---|---|---|
| IPS, no dimming | One light source for the whole image | Raised, grayish blacks | Weak |
| VA panel | Higher native contrast, same single light | Moderate | Usable |
| Mini LED | Hundreds to thousands of zones | Halo at edges | Strong |
| OLED | Per-pixel emission | None | Best blacks |
Local Dimming and Backlight Light Bleed
Local dimming splits the lighting into zones that dim independently. More zones mean less light bleed around bright objects. Judge it in a dark room; ambient light hides the difference.
Turning On HDR Mode in Windows and macOS
Nothing works until HDR mode is on in your system settings:
- Windows 11: Settings, System, Display, then turn on Use HDR. Auto HDR can upgrade many DirectX games.
- macOS: built-in XDR screens switch automatically; for an external display, enable High Dynamic Range in System Settings, Displays.
- The display itself: some models need HDR enabled in their own menu.
Then play known HDR content, such as HDR video or AVIF HDR images, to confirm the switch.
Why SDR Content Looks Washed Out
With HDR on, Windows places SDR content inside an HDR signal. If the SDR content brightness slider in the Windows display settings, or a game's paper white level, is set too low, the desktop looks dim and flat. Many people leave HDR off for office work and enable it only for HDR content such as films and games.
Cables, HDR Gaming and HDR Calibration
- Use HDMI 2.1 or DP 1.4 for 4K HDR at high refresh rates; HDMI 2.0 tops out at 4K 60 Hz.
- For HDR gaming, set each game's peak slider to your display's real output.
- Run the free Windows HDR Calibration app for basic HDR calibration; full calibration needs PQ-aware software and a meter.
- Repeat your HDR testing after any driver or firmware update.
Frequently Asked Questions
- Why does my HDR monitor look bad even though it supports HDR?
- Many monitors accept an HDR10 signal without the hardware to show it. A peak near 400 nits with no local dimming can't hold bright highlights and deep blacks at the same time. Check which VESA DisplayHDR tier the monitor carries: real HDR usually starts at DisplayHDR 600.
- Why does the test say HDR is not detected when my monitor has HDR?
- The browser can only report HDR when the operating system is sending an HDR signal to the display it is on. Turn on Use HDR in Windows or High Dynamic Range in macOS, make sure the browser window is on that display, and run the test again.
- Why does my desktop look gray or washed out after turning on Windows HDR?
- Windows places ordinary SDR apps inside an HDR signal, and the result depends on tone mapping. Raise the SDR content brightness slider in the HDR settings, or switch HDR off for desktop work and back on (Windows + Alt + B) for HDR games and video.
- Which is better, HDR10 or Dolby Vision?
- Dolby Vision uses dynamic metadata and up to 12-bit signals, so it can adjust brightness scene by scene. HDR10 uses static metadata but works everywhere. Use Dolby Vision when your display and app both support it, and HDR10 otherwise.
- Does an 8-bit + FRC panel count as HDR?
- It can accept and show HDR10, using dithering to imitate 10-bit color. Native 10-bit is smoother in fast-changing highlights, but for most people brightness and contrast matter far more than bit depth.
- Can a browser test measure my monitor's peak brightness?
- No. A browser can read capability signals and show comparison patterns, but peak brightness in nits, gamut coverage and local-dimming performance need a colorimeter and HDR test signals.
- Should I keep HDR on for SDR content?
- It depends on how well your display tone maps SDR inside HDR. If SDR apps look dim or washed out, keep HDR off for everyday work and turn it on only for HDR content.