The current JamKazam app is compatible with Windows 10 & 11, and on Mac requires MacOS 10.15 or higher. If your computer won't support the latest JamKazam app, you can still run the JamKazam legacy app (the previous/older version of the app that many users have run for several years now). The new app and the legacy app are mostly compatible and work well with each other (in case some users in a session are on the new app and some on the legacy app), with the exception of video. The new app displays video in a browser window, while the legacy app displays video in an app window, and these don't work together.
If your computer won't support the current/new app, we recommend that your bypass the app update prompt each time you start the JamKazam app.
Windows Users
Windows users will see the prompt below. When you see this prompt, do not click the Start Update button. Clicking this button will start an update to the new app. Instead, press the Control+Shift+N keys (three keys on your computer at the same time). This will close the update prompt and let you keep running the legacy app.
Mac Users
Mac users will see the prompt below. When you see this prompt, click the Esc button. This will close the update prompt and let you keep running the legacy app. 
Getting Back to the Legacy App
If you accidentally update the app and need to get back to the legacy app, we recommend you follow the instructions below.
First, follow the instructions in this help article on how to create a clean install to clean out your JamKazam settings. If you don't do this first, it can cause some problems with clashing settings.
Second, go to this URL in your browser: https://www.jamkazam.com/downloads-legacy. Click the Download button to download the legacy app. When it has downloaded, double click the downloaded file. On Mac, drag and drop the JamKazam app icon onto the Applications icon, and choose the Replace option if prompted. On Windows, follow the on-screen installer instructions.
Third, start up the legacy JamKazam app (skipping the update, per the instructions above), and then set up your audio gear again, using either these instructions for Mac or these instructions for Windows.
When you have done this, you're ready to use the legacy app in online sessions like usual.