Auto HDR Switcher Script for Steam Games (PowerShell)

If you game on Windows and switch between SDR desktop and HDR titles, manual toggling gets old fast. I built a lightweight PowerShell HDR Switcher that watches for Steam games and toggles HDR automatically.

Why I built it

• No heavy third-party tools
• Runs continuously with simple logic
• Fast reaction (~3s polling)
• Built around the native Windows HDR hotkey

How it works

1. A small C# block is loaded in PowerShell to send keyboard events.
2. The script triggers Win + Alt + B (Windows HDR toggle).
3. Every 3 seconds it checks running processes under Steam library paths.
4. Game detected ? toggle HDR on. No game detected ? toggle HDR off.

Script

# Define the HDR Toggle Function
$code = @"
using System;
using System.Runtime.InteropServices;
public class Keyboard {
 [DllImport("user32.dll")]
 public static extern void keybd_event(byte bVk, byte bScan, uint dwFlags, uint dwExtraInfo);
 public static void ToggleHDR() {
 keybd_event(0x5B, 0, 0, 0); keybd_event(0x12, 0, 0, 0); keybd_event(0x42, 0, 0, 0);
 keybd_event(0x42, 0, 2, 0); keybd_event(0x12, 0, 2, 0); keybd_event(0x5B, 0, 2, 0);
 }
}
"@
Add-Type -TypeDefinition $code

$gameRunning = $false

Write-Host "Monitoring for games... (Minimize this window)"

while($true) {
 # This checks for any process running from a "common" Steam library folder
 # Adjust "SteamLibrary" if yours is named differently
 $activeGames = Get-Process | Where-Object { $_.Path -like "*SteamLibrary*" -or $_.Path -like "*steamapps*" } | Where-Object { $_.ProcessName -notmatch "steam|steamwebhelper|overlay" }

 if ($activeGames -and -not $gameRunning) {
 Write-Host "Game detected: $($activeGames[0].ProcessName). Enabling HDR..."
 [Keyboard]::ToggleHDR()
 $gameRunning = $true
 } 
 elseif (-not $activeGames -and $gameRunning) {
 Write-Host "No games detected. Disabling HDR..."
 [Keyboard]::ToggleHDR()
 $gameRunning = $false
 }

 Start-Sleep -Seconds 3 # Faster check (3 seconds)
}

Limitations

• Current detection scope is Steam game paths only.
• HDR uses toggle behavior (no direct state validation in this version).
• Custom Steam library names/locations may need path tweaks.

What I’ll improve next

• Add Epic/Battle.net/Xbox app detection
• Add safe state check to avoid accidental double-toggles
• Package into a cleaner tray-style utility

If you want the next version, I can share a multi-launcher edition with profile-based logic.