Problems · How to check
How do I check if HDR is actually on?
Ask the browser. A page can read whether the system is offering it a high dynamic range surface and which colour gamut, and that is exactly the switch people forget: an HDR capable screen with HDR off in Windows shows every film and game in standard range.
The HDR test on this site reads it in a second. On Windows the switch is under Settings, System, Display; on a Mac it is automatic on a supported display. If the screen is not HDR capable, off is correct, and turning it on for a screen that only accepts the signal makes things worse.
First, notice when it happens
The causes, ranked
1. HDR off in the system
most commonHow to confirm it
The HDR test reads no, on a screen the maker calls HDR.
The fix
Windows: Settings, System, Display, HDR on for that screen. macOS: automatic on supported displays. Then run the test again.
2. Standard content too dim in HDR mode
commonHow to confirm it
HDR reads on, but the desktop and ordinary video look grey and flat.
The fix
Raise the SDR content brightness slider under the HDR settings in Windows. Some screens also need HDR chosen in their own menu.
3. A screen that accepts HDR but cannot show it
commonHow to confirm it
The specification says HDR, the peak brightness is a few hundred nits, and HDR on looks worse than off.
The fix
Leave it off. The HDR label on inexpensive panels means the signal is accepted, not that the panel can show the range.
4. The browser does not report it
occasionalHow to confirm it
Firefox reads unknown; Chrome and Edge report it once the system has it on.
The fix
Check in Chrome or Edge, or trust the system setting; the screen is not at fault.
What the browser can and cannot tell you about HDR
A web page can ask two things through standard media queries: whether the display path offers high dynamic range, and whether it covers a wide colour gamut. Those answers come from the operating system's view of the screen at that moment, so they change when you switch HDR on or off in display settings or move the window to another monitor. That makes them a good check of the switch, and a poor check of the panel.
What no page can read is how bright the screen actually gets, how many dimming zones it has, or whether its black level is deep. A monitor can accept an HDR signal and still show it with limited brightness, which is why HDR sometimes looks flat. For the panel itself, use the black level and local dimming tests on this site with the room dark, and read the screen's own specification from its maker.
Measure it instead of guessing
The HDR test reads whether the browser is offered high dynamic range and which gamut, in a second, without asking you anything. It cannot measure a nit, and says so; it can tell you whether the switch is on.
What software cannot tell you here
- A page cannot measure peak brightness, contrast or the panel's true gamut; that needs a meter on the screen.
- It cannot tell a screen that shows HDR well from one that merely accepts it; the maker's peak brightness figure and a reviewer's measurement can.
Asked, in people’s own words
- Why does HDR look washed out on Windows?
- Standard content is shown at a fixed brightness inside the HDR range. Raise the SDR content brightness slider in the HDR settings and check the screen's own HDR mode.
- Should I turn HDR on for gaming?
- On a screen that can show it, yes, for games that support it. On a screen with low peak brightness, no; the picture is flatter than standard range.
- Can a browser show HDR video?
- Chrome and Edge can when the system has HDR on and the screen supports it, which is what the test reads. Safari on a supported Mac can too.
- Why does the HDR test say no when Windows says HDR is on?
- Usually because the browser window is on a different monitor from the one with HDR enabled, or because the browser has hardware acceleration turned off. Move the window, check the browser's graphics acceleration setting, and reload the page.