guide

How to capture system audio for vizz.fm

It's possible to route your computer's audio output directly into vizz.fm using a virtual audio device. This allows any music you play on Spotify, YouTube, Apple Music, or anywhere else to become a live input for your visualizer. Unlike a microphone, you get a direct lossless feed with full fidelity.

In this guide

How it works macOS Options

Loopback (paid, easiest)BlackHole (free)

Windows Options

VoiceMeeter (free)VB-Audio Virtual Cable (free)

Using it with vizz.fm Troubleshooting

How it works

The concept is the same on every operating system. You need a piece of software that creates a virtual audio device (a fake sound card that exists only in software). You then configure your system to send audio to this virtual device (either exclusively or alongside your real speakers), and tell vizz.fm to use it as its microphone input.

Your Music App (Spotify, YouTube, etc.)

↓

System Audio Output

↓

Virtual Audio Device (the bridge)

↓

vizz.fm “Microphone” Input

↓

Visualizer reacts to your music

macOS Options

Option 1: Loopback by Rogue Amoeba

Loopback

macOSPaid (~$118)

The gold standard for audio routing on Mac. Loopback gives you a visual, drag-and-drop interface for creating virtual audio devices and routing audio between any combination of apps and hardware. It's dead simple and just works.

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Loopback is the option I personally use. It's not free, but it's far and away the easiest to set up. If you don't want to mess around with system utilities, this is the one.

Install Loopback

Download and install Loopback from rogueamoeba.com. You'll need to grant it permissions in System Settings > Privacy & Security.

Create a virtual device

Open Loopback and click the + button to create a new virtual audio device. Give it a recognizable name like “vizz.fm input”.

Add an audio source

In the Sources column, select the audio source you want to route. And then optionally add a Monitor device to hear the audio through your speakers as well.

Select it in vizz.fm

Open vizz.fm, click the audio source button, and choose Microphone. Your browser will ask which microphone to use. Select your Loopback virtual device from the dropdown. Done.

Option 2: BlackHole

BlackHole

macOSFree

A modern, open-source virtual audio loopback driver. Zero latency, supports all standard sample rates, and works on both Intel and Apple Silicon. Requires a bit more manual setup via macOS Audio MIDI Setup.

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BlackHole is the go-to free option. It's lightweight, well-maintained, and trusted by the community. The tradeoff is that you need to configure it manually using macOS's built-in Audio MIDI Setup utility.

Install BlackHole

Download from existential.audio/blackhole or install via Homebrew:

brew install blackhole-2ch

The 2-channel version is all you need for stereo audio. 16ch and 64ch versions are available for more complex routing.

Create a Multi-Output Device

This step lets you hear audio through your speakers and route it to vizz.fm at the same time.

Open Audio MIDI Setup (search for it in Spotlight, or find it in Applications > Utilities)
Click the + button in the bottom-left and select “Create Multi-Output Device”
Check the box for your Built-In Output (or your headphones/speakers) first (this must be the top/primary device)
Then check BlackHole 2ch
Enable Drift Correction for BlackHole (check the box in the Drift column)

You can right-click the Multi-Output Device to rename it to something like “Speakers + Vizz.fm” for clarity.

Set your system output

Go to System Settings > Sound > Output and select your new Multi-Output Device. Audio will now play through your speakers and simultaneously get routed to BlackHole.

Select BlackHole in vizz.fm

Open vizz.fm, click the audio source button, and choose Microphone. When your browser asks which mic to use, select BlackHole 2ch. You should immediately see the visualizer react to whatever you're playing.

If you don't need to hear the audio through your speakers (e.g., you're wearing headphones connected via Bluetooth), you can skip the Multi-Output Device and just set BlackHole as your system output directly. Just remember to switch it back when you're done.

Other macOS options

Audio Hijack (also by Rogue Amoeba, ~$72) is another excellent tool that can capture audio from specific applications. It's more focused on recording than routing, but it can create virtual devices as well. Worth considering if you want fine-grained per-app audio capture.

Windows Options

Option 1: VoiceMeeter

VoiceMeeter

WindowsFree (donationware)

A full-featured virtual audio mixer that installs virtual audio I/O devices on your system. It can mix multiple audio sources, route them to different outputs, and present them as microphone input to any application including your browser.

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VoiceMeeter is the most popular option on Windows. It comes in three versions: VoiceMeeter (basic), VoiceMeeter Banana (more channels), and VoiceMeeter Potato (full-featured). The basic version is all you need for this use case.

Install VoiceMeeter

Download from vb-audio.com/Voicemeeter and run the installer. You must restart your computer after installation for the virtual audio drivers to register.

Configure VoiceMeeter

Open VoiceMeeter after restarting
In the Hardware Out section (top right, A1), select your real speakers or headphones (this is where you'll hear audio)
VoiceMeeter automatically creates virtual input and output devices that Windows can see

Set Windows audio output

Go to Settings > System > Sound > Output and set your output device to “VoiceMeeter Input”. This routes all system audio through VoiceMeeter.

You should see the level meters in VoiceMeeter react when you play music. If you can hear the audio through your speakers, the routing is working.

Select VoiceMeeter Output in vizz.fm

Open vizz.fm in your browser, choose Microphone as the audio source, and when the browser asks which mic to use, select “VoiceMeeter Output”. The visualizer should immediately start reacting to your audio.

VoiceMeeter must be running for the audio routing to work. You can set it to launch on startup via its Menu > System Tray option so you don't have to think about it.

Option 2: VB-Audio Virtual Cable

VB-Audio Virtual Cable

WindowsFree (donationware)

A simpler alternative that just creates a virtual audio cable: a pipe from an output to an input. Less features than VoiceMeeter but easier to configure if you just need basic routing.

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If VoiceMeeter feels like overkill, VB-Audio Virtual Cable is a lighter option from the same developers. It creates a single virtual cable that pipes audio from output to input. The setup is simpler: install it, restart, set “CABLE Input” as your Windows output device, and select “CABLE Output” as your mic in vizz.fm.

Heads up: With VB-Audio Virtual Cable alone, you won't hear the audio through your speakers. It gets routed entirely to the virtual cable. If you need to hear it too, use VoiceMeeter instead, which handles both routing and monitoring.

Using it with vizz.fm

Once you have a virtual audio device set up, the process in vizz.fm is the same:

Open vizz.fm
Click the audio source button to open the source picker
Select Microphone
Your browser will show a permission dialog asking which microphone to use. Select your virtual audio device from the dropdown
Play some music on your computer, and the visualizer will react to it in real time

If you've previously granted vizz.fm microphone access, your browser will remember that choice and automatically use the same device without showing the device picker again. To switch to your virtual audio device, you'll need to reset the permission: click the lock or tune icon in your browser's address bar, find the Microphone permission, and set it back to “Ask”. Then reconnect in vizz.fm and you'll see the full device dropdown.

Why “Microphone” and not a separate option? Browsers treat all audio input devices as microphones via the Web Audio API. They don't distinguish between a physical mic and a virtual audio device. So when vizz.fm asks for microphone access, your virtual device shows up right alongside your real mic. There's no difference from the browser's perspective.

Troubleshooting

Still having issues? Get in touch. I'm happy to help.

Good to go?

Once your virtual audio device is set up, head back to the app and start visualizing.

Launch App