ABI is Application Binary interface. ABI Stability helps communicate binaries even has different version of compiler.

Swift ABI Stability allows the App communicate with Swift Framework  without version sameness. That means we don`t have to embed Swift Framework inside of each apps. App will use Swift Framework embeded on OS.

Swift ABI Stability supported Swift version 5.0, iOS 12.2 above.

Reference https://swift.org/blog/abi-stability-and-more/https://developer.apple.com/videos/play/wwdc2019/402/