Google has rolled out the final Beta build for Android 13. Beta 4 obviously does not introduce any new features, it just focuses on bug fixes and optimizations ahead of the general release of the OS.
Android 13 beta RSS
Google has rolled out Android 13 Beta 3, hitting Platform Stability. This means that all APIs and app-facing behaviors have been finalized and developers should complete compatibility testing of apps.
Google has released Android 13 beta 2 for select devices. Several of Google's device-maker partners have also made the software available and if you qualify you should be able to download it now.
The first public beta for Android 13 is now out. Compatible Pixel users can install the new Android version on their devices starting today, although most features are developer-focused.