Swift is Apple’s programming language for building apps across its platforms. Apple introduced it on June 2, 2014, alongside the iOS 8 SDK. The announcement described Swift as “a powerful new programming language for iOS and OS X” that combines “the performance and efficiency of compiled languages with the simplicity and interactivity of popular scripting languages.”
The language was designed as a safer, more modern replacement for Objective-C, which had been Apple’s primary development language for decades. Apple’s announcement stressed that Swift “helps developers write safer and more reliable code by eliminating entire categories of common programming errors,” while still coexisting with Objective-C so developers could integrate it into existing apps gradually. Xcode Playgrounds, launched at the same time, let programmers see the output of their code instantly as they typed.
Swift was led by Chris Lattner, the creator of LLVM, and is built on the LLVM compiler infrastructure. Lattner records that he began the language in 2010 before a broader team joined the effort.
In December 2015 Apple released Swift as open source. According to the project’s own history, “On December 3, 2015, the Swift language, supporting libraries, debugger, and package manager were published under the Apache 2.0 license with a Runtime Library Exception, and Swift.org was created to host the project.” This moved Swift beyond Apple’s platforms and opened it to use on Linux and other systems.