The Foundation Project, providing core utilities, internationalization, and OS independence

The libdispatch Project, (a.k.a. Grand Central Dispatch), for concurrency on multicore hardware

Twitter Image Pipeline is a robust and performant image loading and caching framework for iOS clients

Open-source implementation of a substantial portion of the API of Apple CryptoKit suitable for use on Linux platforms.

TLS Support for SwiftNIO, based on BoringSSL.