How to read your HDR test results
- HDR active: Yes means the operating system is sending an HDR signal and the browser can display HDR images and video right now.
- HDR active: No on an HDR monitor usually means HDR is switched off in the system settings, the cable or port doesn't support it, or the laptop is on battery.
- Color gamut tells you how wide a range of colors the screen accepts: sRGB is standard, Display P3 is common on newer laptops and phones, Rec. 2020 is the HDR video standard.
- Color depth of 30 bits (10 per color) helps HDR gradients stay smooth; 24 bits can still show HDR with dithering.
What the brightness steps tell you
The blocks are an HDR image the page builds in your browser, encoded with the same PQ curve that HDR films and games use. The first block, 203 nits, is the reference level for normal white in HDR video. Every block after it is a highlight.
| What you see | What it means |
|---|---|
| First blocks grey, the rest white, nothing brighter than page white | HDR is not active, or the browser doesn't display HDR images. The browser is squeezing the HDR image into normal brightness. |
| Blocks get brighter up to about 400–600, then stop | Entry-level HDR (often sold as HDR400). Highlights are limited. |
| Blocks keep brightening to 1000 or beyond | A strong HDR screen, such as a good mini-LED or high-end OLED TV or laptop. |
| Blocks look bright but the page white is dim | Normal: Windows keeps SDR content at a lower level inside HDR mode. |
Small bright areas often get brighter than large ones, especially on OLED screens, so use full screen as well for a second look.
How to turn on HDR
- Windows 11: Settings › System › Display › select the monitor › turn on Use HDR. Use the "SDR content brightness" slider if normal windows look too dim. Laptops may need "Allow HDR on battery" in the same menu.
- macOS: MacBook Pro and Pro Display XDR screens show HDR automatically. For external monitors, open System Settings › Displays and turn on High Dynamic Range.
- Phones and tablets: recent iPhones, iPads and many Android phones show HDR automatically in supported browsers.
- Cable: 4K HDR at high refresh rates needs DisplayPort or an HDMI 2.0 or newer cable and port.
Checking the panel itself? The dead pixel test finds stuck pixels, the backlight bleed test shows light leaking at the edges, and the OLED burn-in test reveals image retention.
How we tested this tool
We ran the HDR test in Chrome on a standard (SDR, sRGB, 8-bit) laptop screen: it correctly reported HDR off, sRGB and 24-bit color, and the HDR video check returned the browser's real answer. We checked the brightness encoding against the PQ standard (203 nits → 0.581, 1000 nits → 0.752, 10000 nits → 1.0) and confirmed the generated 16-bit HDR image decodes at full size and is read as PQ: on our SDR screen the steps came out as rising greys that clip to white at 1000 nits, as expected from tone mapping. We have not yet viewed the page on an HDR screen, so we can't show you how the steps look there; tell us through the contact page what your screen showed.
Frequently asked questions
Why does the HDR test say HDR is off when my monitor supports HDR?
On Windows, HDR has to be switched on in Settings, System, Display, Use HDR, and laptops often turn it off on battery. The browser only reports HDR while the operating system is actually sending an HDR signal to the screen. Turn it on and reload the page.
What does 203 nits mean in the brightness steps?
203 nits is the reference level for normal white in HDR video (ITU-R BT.2408). The other steps are highlights above that. On a real HDR screen they glow brighter than the white page until the screen reaches its peak brightness.
Can this HDR test measure my screen's exact peak brightness?
No. It shows where the steps stop getting brighter, which gives a rough idea of the peak, but the screen's tone mapping, dimming zones and the brightness settings all affect what you see. Exact numbers need a colorimeter.
My screen says HDR but the colors look washed out. Why?
Windows shows normal (SDR) content inside HDR mode with a separate brightness slider, and low-cost HDR400 monitors often look flat. Adjust the SDR content brightness in Windows HDR settings, or keep HDR off for desktop work and turn it on for games and videos.
Do I need HDR to see the wide color test?
No. Wide color (Display P3 or Rec. 2020) is separate from HDR brightness. Many laptops and phones show P3 colors without HDR, so the right half of each swatch looks more vivid on them.