Turns out that for the many things Macs are good for, getting computer audio to stream is a bit tricky due to some technical limitations (when compared to Windows). This means that if you want to share a movie or video with a friend from the desktop app, they might not hear the audio.
Use Kast Web
We recently released a new big update for Kast Web, which allows you to stream directly from the web app. This allows you to share the audio from Mac more easily than on the desktop app. Read more about Kast web here or visit https://w.kast.live/ to start kasting.
Black Hole (free)
Black Hole is a free third party application for Mac audio management.
Disclaimer: this suggestion uses external software that we have no control over. Therefore, please proceed with the suggestion at your own risk.
Step 1: You can download the installer from : http://existential.audio/blackhole/
***The installer will be sent to the email address entered.
Step 2: Once downloaded, close out all applications on your computer including your web browser and Kast.
Step 3: Follow installation instructions here: https://github.com/ExistentialAudio/BlackHole/wiki/Installation
Step 4: Search for "Audio Midi Setup" through your spotlight (command + space)
Step 5: Open Audio Devices Window.
***If this screen does not appear, select Audio Devices from the Windows drop down menu in Audio Midi Setup.
Step 6: Create a Multi Output Device by clicking the + icon In the lower left hand corner of the Audio Devices. Select Create Multi-Output Device
Step 7: In the new Multi-Output device you just created select the audio devices that you want to output audio. It is highly recommended you enable "Drift Correction" for all devices except the Clock Source device.
***Due to issues with macOS the Build-in Output (sometimes called MacBook Pro Speakers or similar) must be enabled and listed as the top device in the Multi-Output. If BlackHole is listed first simply uncheck and recheck the box under "Use" to change the order.
Step 8: Set Audio Output to Multi-Output Device
Right click on your Multi-Output device and select "Use This device For Sound Output. Audio should now be playing through your speakers.
***If you did not close your browser because you were following this guide, close it out and restart it now.
Step 9: Open Kast -> Enter a party -> Go to your Audio Settings in Kast and Change your "Microphone / Input" to "BlackHole 16ch (Virtual Cable)"
Ensure that your Mic is set to "Open" and that the "Unmute / mute yourself" button is not crossed out.
Step 10: You're finished! You can now share your videos audio!
Loopback Audio ($99)
Getting audio to work properly using Loopback Audio is very easy. However, Loopback Audio is fairly expensive. For the trial version, the sound will get a noise overlay after 20 minutes, which does not sound nice.
Step 1: Download Loopback Audio from: https://www.rogueamoeba.com/loopback/
Step 2: Install the software by running the installer you just downloaded. It should work out-of-the-box.
Step 3: With Loopback Audio installed, time to set it up. Initially you will see this view:
Step 4: Next to "Sources", click the plus button and select the app from which you want to stream the sound. We are using Chrome in this example.
We're watching the Old Town Road music video for the 57th time on YouTube, so you can see those green left/right channel bars indicate there is some sound coming from Chrome. A good sign, partner!
When you add an application, Loopback will automatically create routing to "Channels 1 & 2".
Step 5: Back in Kast, select Loopback audio for the "Microphone / Input" in the sound options, shown in the image below:
Step 6: You are done! Enjoy your new found audio awesomeness
Phew, thanks for sticking through that, hopefully you should now be able to do what you actually want: share awesome content with your friends!