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HDR Test

See how bright your HDR setup gets. Compare SDR white with HDR patches from 203 to 10,000 nits or a level you type in, check how much the screen dims big bright areas, and count near black steps. It runs in your browser and measures nothing.

Your setup

Screen reports HDR
Checking
Browser shows HDR images
Checking
Widest color range
Checking

Checking what this browser and screen report.

Which test?

SDR white and eight HDR levels from 203 to 10,000 nits, in small patches on black.

Before you start

  • Use Chrome, Edge or Safari 26 or newer. Firefox doesn't show HDR images yet.
  • Windows: turn on Use HDR in Settings, System, Display. The SDR content brightness slider there moves SDR white, and the HDR patches move with it.
  • Mac: built-in XDR screens show HDR on their own. For an external HDR monitor, turn on High Dynamic Range in System Settings, Displays.
  • Put the monitor in its HDR mode, and turn off eco or power saving modes that cap brightness.
  • Dim the room, and give your eyes a minute before the near black test.

Brightness steps. Find the last patch that's still brighter than the one before it. Past that point your setup can't go brighter, so the rest look the same.

This browser can't open fullscreen here, so the test fills the browser window. Fullscreen works best, since page colors around the patches change how bright they look. Press H to hide the controls, F for fullscreen and Escape to leave. In the compare and window tests, the arrow keys change the right patch or the box size.

Shopping for an HDR monitor? The HDR Label Decoder shows what each DisplayHDR tier asks for and what HDR10, HDR10+, Dolby Vision and HLG mean.

What to look for

What the brightness steps test shows, what's normal, and what it can't tell you.

On screen
SDR white and eight HDR levels from 203 to 10,000 nits, in small patches on black.
Look for
Find the last patch that's still brighter than the one before it. Past that point your setup can't go brighter, so the rest look the same.
Usually normal
Where the steps stop depends on the screen and your settings. On most monitors the last few patches look the same. The top DisplayHDR tier asks for 1,400 nits, so anything above that is past what monitors are certified for.
Can't tell you
It can't give you a nit reading. The browser and OS tie the signal to your SDR brightness setting and squeeze what the screen can't reach, so the step where it stops moves when you change those settings.
  • SDR white. Plain #FFFFFF, the brightest white a normal page can show.
  • 203 nits. HDR reference white in ITU-R BT.2408, the level for a white page or paper white in HDR.
  • 400 nits. The peak DisplayHDR 400 and True Black 400 ask for.
  • 600 nits. The peak DisplayHDR 600 and True Black 600 ask for.
  • 1,000 nits. The peak DisplayHDR 1000 and True Black 1000 ask for, and a common mastering level for HDR video.
  • 1,400 nits. The peak DisplayHDR 1400 and True Black 1400 ask for.
  • 2,000 nits. Brighter than any DisplayHDR tier asks for.
  • 4,000 nits. A mastering level some HDR films use for their brightest highlights.
  • 10,000 nits. The top of the PQ signal range.

Limits of any browser HDR test

  • Nothing here measures light. For real nit readings you need a colorimeter, or a review that used one.
  • The browser, the OS and the monitor's own tone mapping all change what you see, so the same patches can look different on the same screen with other settings.
  • Screenshots and screen recordings of these patches don't show what your screen shows.

How to use this tool

  1. Turn on HDR and open a browser that shows it

    Turn on HDR in your OS display settings and put the monitor in its HDR mode. Use Chrome, Edge or Safari 26 or newer. The Your setup box says whether the screen reports HDR and whether the browser can show HDR images.

  2. Pick a test

    Brightness steps puts SDR white and eight HDR levels side by side. Compare two levels puts any two next to each other. Window size shows one level in a box from 2% to the full screen, and Near black shows very dark patches on black. In the compare and window tests, Custom lets you type in your own level in nits.

  3. Start it full screen and hide the controls

    Press Start fullscreen, then press H or tap the screen to hide the controls, since their box adds light of its own. In the compare and window tests, the arrow keys change the right patch or the box size.

  4. Read what you see

    Find the last step that still gets brighter, watch whether a big box gets dimmer than a small one, and count the near black patches you can see. Press Escape to leave. The guide under the tool says what's normal for each test.

About this tool

This HDR test shows real HDR patches in your browser, next to plain SDR white. If your screen, OS and browser are all in HDR, the patches get brighter than anything a normal web page can show, up to the point where your setup runs out. That point is what the tests help you find.

It's a tool for looking, not a meter. The levels are signal values, the same way a movie asks for a brightness, and the browser and screen decide what you get. The guide says what each test can and can't tell you.

How the patches work

Each patch is a tiny PNG image with PQ values, the same transfer curve HDR10 and Dolby Vision use. A cICP tag marks it as BT.2100 PQ, and a light level tag gives its own brightness, so the browser handles each patch on its own. SDR white is a plain #FFFFFF box.

Chrome, Edge and Safari 26 show these images in HDR when the screen and OS are in HDR mode. They squeeze anything above what the screen reports it can show, and Chrome and Edge put HDR reference white at about the level of SDR white.

How it relates to the other screen tools

The HDR Label Decoder explains what the DisplayHDR tiers and the HDR10, HDR10+, Dolby Vision and HLG logos on a box mean. The Monitor Test covers SDR checks like dead pixels, banding and backlight bleed. The Display Bandwidth Calculator shows whether your cable can carry 10-bit HDR at your resolution and refresh rate.

What isn't in it

No nit readings, calibration or tone mapping curves. Those need a colorimeter. No HDR video either: Dolby Vision and HDR10+ dynamic metadata only work in video players, so this test can't tell whether your screen decodes them.

HDR testing guides

How to set up and test an HDR screen, what the nit levels mean, and why HDR can look wrong.

How to test an HDR monitor
Turn HDR on in the right places, then use brightness steps to see where your screen stops getting brighter.
View details
What nits mean for HDR
A nit is one candela per square meter. Here's where SDR white, HDR reference white and the DisplayHDR tiers sit.
View details
HDR looks washed out
Gray blacks and dull colors in HDR mode usually come from settings, not a broken screen. Here's what to check.
View details

Frequently asked questions

Why do the HDR patches look the same as SDR white?
Something in the chain isn't in HDR. Check that HDR is on in your OS display settings, that the monitor is in its HDR mode, and that you're using Chrome, Edge or Safari 26 or newer. Firefox doesn't show HDR images yet. On a laptop, Windows can turn HDR off on battery. If the Your setup box says No for both lines, no patch can get brighter than SDR white.
Can this test tell me how many nits my monitor reaches?
No. The labels are the brightness each patch asks for, not what the screen shows. The browser and OS tie the HDR signal to your SDR white level and squeeze anything the screen says it can't reach. The point where the steps stop tells you where your whole setup tops out. For a real reading you need a colorimeter, or a review that used one.
Why does 203 nits look about the same as SDR white?
203 nits is the HDR reference white in ITU-R BT.2408, the level a white page or paper white should sit at in HDR. Chrome and Edge show it at the same brightness as SDR white, so a white page doesn't jump when HDR content appears. Other browsers can put it a little higher. Either way, the real HDR headroom starts above it.
Can I test a nits level that isn't on the list?
Yes. In the compare and window tests, press Custom and type any whole number from 1 to 10,000 nits. It's handy for checking a number from the box or a review: put the peak your monitor claims next to a higher level and see whether the higher one still gets brighter. Shared links keep the level you typed.
Why does the big box in the window test get dimmer?
Most HDR screens limit how much light they put out at once, to stay within their power and heat limits. A small highlight can hit the peak, while a full white screen gets less. OLED panels usually dim more than LCDs. VESA's DisplayHDR tiers allow for this too: every tier asks for less on a full screen held for a while than on a small patch.
Is this the same as a DisplayHDR certification test?
No. VESA tests with a colorimeter and set patterns, and checks far more than brightness. This test shows what your setup does with HDR signals, by eye. To see what a DisplayHDR tier on the box asks for, open the HDR Label Decoder.
Is anything saved or sent anywhere?
No. The patches are small images made in your browser. Shared links only carry the test and its levels, never what your browser reports or anything you saw, and a shared link always starts at the setup screen.

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