Sound
You may need to set up some sort of virtual audio driver to route audio from your browser windows and any other apps (e.g. if applying effects via a DAW) into OBS – when I was on a Mac, I used SoundFlower and had a Multi-Output Device set up so I could both hear the audio and route it into OBS. To set up a Multi-Output Device on Mac, see this document: https://support.apple.com/en-gb/guide/audio-midi-setup/ams7c093f372/mac
Windows doesn’t seem to need anything additional to receive computer sound
Cropping & resizing
- Crop a window by holding Alt and dragging the bounding box (be sure the bounding box isn’t set in the Transform dialogue)
- Resize a window by just dragging its corners
- You can capture the same window multiple times and apply different crops and resizes each time to, for example, separate out users in a single videoconference.
- Note that once a window is cropped in OBS, if you move it from its original position on your screen, the crop in OBS may no longer reflect the section you want to see.
- If you’re wanting to capture a browser window without the chrome (all the tabs and address bar, etc), you can hide this in Google Chrome with F11 (or if your computer is paranoid about its F-keys like mine is, Fn-F11). This could be especially useful if using OBS to stream from Google Meet as you can make the browser take up the whole screen so you don’t need to crop out the chrome.
Google Meet → OBS
Cropping can be useful for making adjustments to Google Meet windows where participants can’t be hidden – crop to just the presentation area.
Test your cropping carefully – when Google Meet is muted, it has a tendency to pop up a message asking if you’re trying to say something – this message intrudes into the frame area and cannot be disabled.
Zoom → OBS
Use Computer Audio
Share Computer Sound for presentation mode
On the Host’s computer (the person collating material in OBS), you’ll need to take the Zoom window off full screen or (in our experience – let me know if yours differs) OBS won’t be able to show it in the dropdown to be selected
Using multiple videoconference instances
For Zoom, you cannot log into multiple meetings simultaneously from a free or pro account – multiple simultaneous Zoom meetings require Business, Enterprise or Education account. Obviously this can be solved with upgrading account type – hopefully only 1 person (the one using OBS) would need this, but the need for it is probably limited to where multiple performers need to share their screens simultaneously *with audio*. OBS can offer ways around this, though, allowing ‘daisy-chaining’ of videoconference instances without needing to pay for upgrades.
We have not tested Google Meet in such a configuration since they’ve implemented computer audio, but we have combined presenting with computer audio from Zoom with multiple instances of presenting via mic in Google Meet, as in the example.
Example

Alexander Schubert’s Browsing, Idling, Investigating, Dreaming (Bastard Assignments Lockdown Jams, 2020):
This piece is performed live using 1 Zoom meeting (browser-based Spotify), 2 Google Meet meetings (Google StreetView is silent, the computer voice uses the system mic – voice suffers a bit less badly through the mic than music or other sounds because the tool prioritises voices) and 1 local browser window (field recordings), aggregated in OBS and the OBS output then pushed out to the other three performers via an additional Google Meet meeting. Due to feedback problems, however, the field recordings are not heard by the other performers (although I’m sure there’ll be a way I can rectify this). Additionally, everyone joined the Zoom meeting as this was the easiest way to communicate without interfering with the other setups. The setup diagram is as follows:

See the live-recorded video:
Dealing with feedback problems
First check everybody’s mics are muted everywhere (or everywhere but 1 source)
Go into Settings > Audio in OBS and check the Monitoring section. You should be monitoring only something that doesn’t have an audible output otherwise, while system audio may need to go to a multi-output device (speakers and Soundflower)
Check your sound sources and outputs at the system level, in OBS AND where another tool has separate settings, e.g. Zoom lets you specify different outputs within the tool and doesn’t necessarily change them when your system settings change.