SndVolWeb — Real Windows Volume Mixer Web App

A web-based replica of sndvol.exe that controls REAL Windows audio — your actual speakers and every running app's audio session (Chrome, Spotify, Discord, VLC, etc.) — using the Windows Core Audio (WASAPI/MMDevice) API through NAudio.

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How it works

Browser UI  ←──────────────→  ASP.NET Core API  ←──→  Windows MMDevice API
(your browser at localhost:5050)   (runs on your PC)        (real audio)

The backend uses NAudio (a .NET wrapper for Windows Core Audio COM APIs):

• MMDeviceEnumerator → lists real audio endpoints
• AudioEndpointVolume → master device volume & mute
• AudioSessionManager2 → per-app audio sessions
• ISimpleAudioVolume → per-app volume & mute
• Process.GetProcessById → resolves PID → app name/icon

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Prerequisites

Requirement	Version	Link
.NET 8 SDK	8.0+	https://dotnet.microsoft.com/download
Windows	10 / 11	(required — uses Windows Core Audio)

Check if .NET is installed:

dotnet --version
# Must print 8.x.x

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Setup & Run (Step by Step)

Step 1 — Extract the project

Unzip SndVolWeb.zip to any folder, e.g. C:\SndVolWeb\

Step 2 — Open a terminal in the project folder

cd C:\SndVolWeb

Step 3 — Restore packages (downloads NAudio from NuGet)

dotnet restore

You'll see it download:

  Restored ... NAudio (2.2.1)
  Restored ... NAudio.Wasapi (2.2.1)

Step 4 — Run

dotnet run

Output:

info: Now listening on: http://localhost:5050

Your browser opens automatically at http://localhost:5050

You'll see your real speakers and every app currently playing audio!

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What you'll see

Channel	What it is
Speakers	Your default audio device — drag to change master volume
System Sounds	Windows notification sounds (PID 0)
Chrome / Edge	Any browser tab playing audio
Spotify	Spotify app if it's open
Discord	Discord voice/sounds
Any other app	Anything registered with Windows audio mixer

🔄 The UI auto-refreshes every 4 seconds to detect new/closed app sessions, just like the real sndvol.exe.

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Build as a standalone .exe (no .NET install needed)

dotnet publish -c Release -r win-x64 --self-contained true -o .\publish

Then just run:

.\publish\SndVolWeb.exe

It opens your browser automatically!

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Troubleshooting

"No audio device found" → Make sure your PC has an audio device and it's enabled in Windows Device Manager.

"No active app audio sessions" → Open an app that plays sound (Chrome with a YouTube tab, Spotify, etc.) then click ↻ Refresh or wait 4 seconds.

"Cannot reach the audio API" → The dotnet run server isn't running. Start it first, then open the browser.

Firewall prompt → Click "Allow" — it only listens on localhost (127.0.0.1), not accessible from other computers.

"Access denied" errors → Run the terminal as Administrator if NAudio can't access audio sessions.

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API Reference

Method	URL	Body	Description
GET	/api/volume	—	All real channels
PATCH	/api/volume/{id}/volume	{"value":75}	Set volume 0–100
PATCH	/api/volume/{id}/mute	{"muted":true}	Mute/unmute

IDs look like:

• Device: device:{windows-device-guid}
• App: session:{pid}:{appname}

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Add more app icons

In wwwroot/js/app.js, add to the ICONS object:

myapp: () => `<svg>...</svg>`,

In WindowsAudioService.cs, add to _iconMap:

["myapp"] = "myapp",

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License

MIT — free to use, modify, and distribute.

👤 Author

Hadi Cahyadi

Support me on Patreon