# Windows HDR: the whole chain has to support it

> Why HDR stays off or looks washed out: panel capability, cable bandwidth, EDID, Windows settings and per-app tone mapping.

**Tested on**

- Build: 26300.9457
- Edition: Pro (26H2)
- Architecture: x64
- Evidence: E1
- Verified: 2026-10-29

## The short answer

HDR needs **five** things to line up:

1. a panel that actually meets the brightness/contrast requirements (not just "HDR compatible");
2. enough **link bandwidth** for the resolution, refresh rate and colour depth;
3. a **cable and port** rated for it;
4. an **EDID/monitor capability** block that Windows can read;
5. Windows HDR **enabled per display**, plus per-app handling.

Break any one and you get: HDR greyed out, HDR enabled but washed out, or HDR that only works in one app.

## Check the link budget first

HDR at 4K/120 with 10-bit colour needs far more bandwidth than 4K/60 8-bit. That is why HDR works on one port and not another on the same GPU.

| Resolution/refresh | Practical requirement |
|---|---|
| 4K 60 Hz, 8-bit | HDMI 2.0 or DP 1.2 is usually enough |
| 4K 60 Hz, 10-bit HDR | HDMI 2.0 at the edge; DP 1.4 comfortable |
| 4K 120 Hz, 10-bit HDR | HDMI 2.1 or DP 1.4 with DSC |
| 1440p 240 Hz, HDR | DP 1.4 with DSC, or HDMI 2.1 |

If the port runs out of bandwidth, the driver silently reduces refresh rate or colour depth — and Windows may then refuse HDR.

```powershell
# enumerate displays and their modes
Get-CimInstance -Namespace root\wmi -ClassName WmiMonitorID |
  Select-Object InstanceName,ManufacturerName,UserFriendlyName,YearOfManufacture
Get-CimInstance Win32_VideoController | Select-Object Name,CurrentHorizontalResolution,CurrentVerticalResolution,CurrentRefreshRate,CurrentBitsPerPixel
```

`CurrentBitsPerPixel` below 30 (10-bit) on an HDR-capable display is the tell that the link or mode negotiated down.

## EDID and the monitor driver

Windows learns what a display can do from **EDID**, delivered through the monitor driver. Problems:

- a **generic monitor driver** may hide HDR capabilities;
- **cheap KVM switches and extension cables** corrupt EDID, and the display falls back to a safe mode;
- **adapters** (DP→HDMI) may not pass HDR metadata.

Installing the vendor's monitor driver (or a correct `.inf`) sometimes restores options that the generic driver hid. `Get-PnpDevice -Class Monitor` shows which driver is bound.

## Turn it on, then calibrate

1. **Settings → System → Display → HDR** — enable per display.
2. **Windows HDR Calibration** app — sets peak brightness and tone mapping for that panel.
3. **Auto HDR** — converts SDR games; quality varies by title.
4. **SDR content brightness** slider — controls how bright normal desktop content looks while HDR is on.

The washed-out look people report is usually SDR content being tone-mapped by a profile that does not match the panel. Calibration fixes it far more often than a driver update.

> **Caution: HDR on all the time is a preference, not a requirement**
>
> Leaving HDR enabled makes SDR desktop content depend on the SDR brightness slider and the panel's tone mapping. Many people prefer HDR only for games/video (Win + Alt + B toggles it on current Windows). Both are valid; neither is "correct".

## When HDR is greyed out

Check, in this order:

1. The display is connected to a port that supports the mode (not through a hub/dock that downgrades it).
2. The cable is rated (Ultra High Speed HDMI / DP 1.4 certified).
3. The monitor's own OSD has HDR enabled — many panels require it per-input.
4. Windows sees 10-bit: `CurrentBitsPerPixel ≥ 30`.
5. The GPU driver supports HDR on that output (older GPUs drop it).

## Related

- [Monitor choice and VRR](https://windows.homes/en/hardware/display/monitor-choice/)
- [USB4 and docks](https://windows.homes/en/hardware/display/usb4-dock/)
- [High DPI and scaling](https://windows.homes/en/hardware/display/dpi-scaling/)

## Lab boundary

E1. HDR behaviour is documented by Microsoft and depends on physical panel/cable capability. The lab has no HDR display, so nothing was measured and no calibration numbers are claimed.

## Sources

- [Microsoft Learn — High dynamic range](https://learn.microsoft.com/en-us/windows/win32/direct3darticles/high-dynamic-range)
- [Microsoft Learn — DISPLAYCONFIG_VIDEO_SIGNAL_INFO](https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-displayconfig_video_signal_info)
- [Microsoft Learn — Monitor drivers](https://learn.microsoft.com/en-us/windows-hardware/drivers/display/monitor-drivers)

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Source: https://windows.homes/en/hardware/display/hdr-chain/