Swift 5 is a major milestone in the evolution of the language.

Swift 5 makes shipping apps dramatically better. The Swift runtime is now built right in to iOS, macOS, watchOS and tvOS. Your app no longer needs to bundle this library for these latest OS releases. And with great App Store support, your users will get faster downloads and smaller apps. Additional Features in Swift 5 * String reimplemented with UTF-8 encoding which can often result in faster code * Exclusive access to memory is now enforced by default on debug and release builds * SIMD Vector and Result types added to the Standard Library * Performance improvements to Dictionary and Set * Support for dynamically callable types to improve interoperability with dynamic languages such as Python, JavaScript and Ruby