Super Boring Tools

Search tools

Find a tool by name or what it does.

HDR Display Test

See whether your screen can go brighter than plain white, with the two whites side by side.

Comparison
Brightest whiteOrdinary white

If the two halves look identical, this screen has no headroom above plain white.

What this display reports

Standard dynamic range

This display tops out at ordinary white, so both panels above are the same. A different screen, or turning off low power mode, may change the answer.

Colour gamutUnknown

Comparison mode

Runs in your browser. Nothing is uploaded.

How to test whether a display supports HDR

  1. Look at the two panels

    The left half shows the brightest white the display can produce, the right half shows ordinary white.

  2. Try alternating mode

    Switch to alternating if the two look similar. Swapping the same patch between both whites makes a small difference much easier to catch.

  3. Read what the display reports

    Check the dynamic range and colour gamut the screen is reporting to the browser right now.

  4. Compare fullscreen

    Fill the whole display for the clearest result, and press Esc when you are done.

Why use this tool

A real side by side

Both whites are on screen at the same time, so you judge the difference directly instead of from memory.

Alternating mode

Swaps one patch between the two whites every second, which reveals a gap too small to notice when the panels sit next to each other.

Reports what the browser sees

Shows the dynamic range and the widest colour gamut the display is currently claiming, which updates if you move the window to another monitor.

Catches settings, not just hardware

Low power mode and a low brightness setting can switch the effect off on capable hardware, and this test reflects the state you are actually in.

Nothing to install

No download, no extension, and no account. Open the page and look.

Nothing leaves your browser

The result is read locally. Nothing about your display is sent anywhere.

About this tool

Specification sheets are a poor guide to whether a screen actually delivers a high dynamic range in day to day use. A display may advertise the capability but be running in a mode that disables it, be connected over a cable that cannot carry it, or be sitting at a brightness too low for the effect to appear. The only reliable answer is to look.

This test puts the two whites next to each other. One half asks the display for the brightness it holds in reserve above ordinary white; the other half is ordinary white. On a capable screen in a capable state, the difference is immediate and slightly startling. On a standard screen the two halves are identical, which is itself a clear answer.

If the panels look close, alternating mode helps. Instead of two patches side by side, it swaps a single patch between both whites once a second. Human vision is far better at detecting a change over time in one place than a small difference between two places, so a gap that is invisible in split view often reads as an obvious pulse.

Underneath, the page also reports what the display is telling the browser: whether it currently claims a high dynamic range, and the widest colour gamut it covers, from sRGB through Display P3 to Rec. 2020. Those are separate properties, and a screen can have a wide gamut without any brightness headroom. Once you know your screen has headroom, the white screen puts it to use as a light panel and the HDR QR code uses it for contrast.

Frequently asked questions

Both halves look the same. Is my display broken?
No. It most likely means the display has no brightness in reserve above ordinary white, which is true of most standard monitors and older phones. Check the reported dynamic range below the panels for confirmation.
My screen supports HDR but the test shows no difference.
Several things switch the effect off on capable hardware: low power mode on an iPhone or iPad, a very low system brightness, an external monitor connected in a standard range mode, or a browser that does not pass the capability through. Try raising the brightness and turning off low power mode first.
What is the difference between dynamic range and colour gamut?
Dynamic range is about brightness, specifically how far above ordinary white the display can go. Colour gamut is about how many colours it can show. They are independent, so a screen can cover a wide gamut like Display P3 while having no brightness headroom at all.
Does the result change between browsers?
It can. Support for the video format that carries the bright white varies, and browsers differ in how they report display capability. If one browser shows no difference, another on the same machine may.
Is anything uploaded?
No. The capabilities are read locally in your browser and used only to draw this page. Nothing about your display is sent to a server.
Where does the brighter white come from?
The technique is from Superwhite by dtinth, which found that a tiny video clip asking for high dynamic range headroom renders a white far brighter than a web page can otherwise produce. See github.com/dtinth/superwhite for the original.

Related tools