Version history of Swift
Big source: https://medium.com/@mayurkore4/the-evolution-of-swift-a-journey-through-apples-game-changing-programming-language-ccaca14404d7
This is a short timeline of Swift’s development.
Swift 1.0 (2014)
Introduced at WWDC 2014 as a successor to Objective-C. Swift 1.0 brought improvements desired in Apple’s ecosystem: strong type safety, which catches many errors at compile time; optionals to handle nil values safely (avoiding the notorious null-pointer crashes common in ObjC); type inference to reduce verbosity; and closures and other functional programming paradigms for more expressive code. The language was touted as faster, safer, and more expressive than Objective-C, aiming to combine “the performance and efficiency of compiled languages with the simplicity and interactivity of scripting languages.” But, Swift 1.0 was kinda immature. People noted a lack of stability, limited Objective-C interoperability, and source-breaking changes even in minor updates. Yikes.
Swift 2.0 (2015)
Released at WWDC 2015, Swift 2 focused on stability, performance, and refinement. It introduced a formal error handling model with do/try/catch, replacing Objective-C’s NSError patterns with concise language syntax. This marked a philosophy shift to safer error propagation and handling. Swift 2 also added protocol extensions, allowing default method implementations on protocols. This was a powerful feature enabling protocol-oriented programming* paradigms.
* Protocol-oriented programming is a design paradigm where you define interfaces and default behaviors in protocols and protocol extensions. This promotes flexible composition and code reuse instead of relying on class inheritance.
Another addition was availability checking (compile-time checks for API availability on OS versions) to help maintain backward compatibility. Performance was improved (faster compilation and runtime), and Apple open-sourced Swift in late 2015. Yayyyyy! On December 3, 2015, Swift was released under an Apache 2.0 license, with Apple launching Swift.org and inviting the community to contribute to the language’s evolution. Open sourcing Swift expanded its platform support to Linux (and later Windows-who-wouldda-thought) and signaled a shift to community-driven development.
Swift 3.0 (2016)
A major overhaul, often called a “breaking change” release. Swift 3 aimed to make the language more consistent and idiomatic, guided by the new Swift API Design Guidelines. It featured massive syntax changes and API renaming for clarity and expressiveness. For example, many Objective-C APIs were imported with more “Swifty” signatures (dropping needless parameter names, etc.), and core language syntax was cleaned up (e.g. goodbye to C-style for-loops). This release introduced the Swift Package Manager (SPM) for native dependency management, reflecting Swift’s growing role beyond app scripts to cross-platform libraries. Concurrency got somewhat easier with improvements to Grand Central Dispatch (GCD); Swift 3 included a new, Swifty syntax for GCD queue operations and closures. The price for these improvements was lack of source compatibility: people had to migrate code due to the many breaking changes. Nonetheless, I think Swift 3 laid a foundation for a more regular and future-proof syntax, setting a baseline for source stability thereafter.
Swift 4.0 and 4.2 (2017-2018)
These versions focused on stability, performance, and minor enhancements while maintaining source compatibility with Swift 3. Swift 4 introduced the Codable protocol, simplifying JSON (and plist) encoding/decoding by auto-generating encoders/decoders for data models. This was a shift toward convenience in everyday tasks (e.g., working with REST APIs) without third-party libraries. The string type was made more memory-efficient; Swift 4 strings became a collection of characters (resolving earlier Unicode quirks) and gained support for multi-line string literals, among other improvements. Swift 4.2 (late 2018) brought further performance optimizations, including faster build and compile times, and refined some standard library protocols (like a new Hashable implementation) for consistency. These releases indicate Swift’s shift from “radical” (maybe “big” is a better word) changes to incremental refinement, as the core language matured. Notably, during this period Apple’s OSes began shipping with Swift’s ABI included (though the ABI wasn’t declared stable until Swift 5), hinting at the impending stabilization.
Swift 5.0 (2019)
A release that achieved ABI stability for the Swift runtime and standard library. ABI stability meant that starting with Apple’s iOS 12.2/macOS 10.14.4, the Swift runtime is built into the OS; apps no longer need to bundle Swift’s libraries, and future Swift versions maintain binary compatibility. This was monumental for Swift’s adoption in frameworks and OS components. Swift 5 also introduced high-level features like Result<T, Error> for cleaner asynchronous code and error handling without heavy reliance on completion closures. There were additional String enhancements (memory and performance improvements, plus support for raw string literals to easier handle regex or code generation scenarios). With the ABI stable and source stability goals met, Swift 5.x set the stage for Swift to be used for long-term systems and app development without frequent rewrites.
This is when Apple start using Swift in OS components and frameworks.
Swift 5.5 (2021)
Marked the introduction of Swift’s new concurrency model (there is legit entire books on this), one of the largest shifts in Swift’s design since inception. Swift 5.5 added structured concurrency with async/await syntax for asynchronous functions, and actors** for isolated state.
* Actors are reference types that isolate their mutable state by serializing all access through an asynchronous message queue, ensuring data-race-free interaction.
Imagine each actor as a single bank teller who handles one customer at a time, ensuring no two customers ever get mixed up in a single conversation.
In a threat-detection system, using actors to isolate each network flow’s analysis prevents one malicious packet stream from corrupting or racing with another’s threat counters, ensuring accurate and race-free intrusion alerts.
This aligned Swift with other languages (like Kotlin, C#) embracing async/await, but with a focus on safety: Swift’s async/await is built atop cooperative threading, and actors provide data isolation to prevent data races on shared mutable state. Along with these came task groups and the AsyncSequence protocol, forming a “language-integrated concurrency system.”
* A language-integrated concurrency system is a set of native language features (like async/await, actors, and task groups) that let you express and enforce concurrency patterns at compile time, compared to traditional library- or OS-based approaches (w.g., callbacks, threads, dispatch queues) that live outside the language’s type system.
The addition of concurrency features reflects a design philosophy shift to embrace safe multithreading in the language, moving beyond GCD’s manual thread management to a more structured approach. This has huge implications for macOS app devs (and server devs alike), making concurrent code simpler and less error-prone.
Swift 5.6-5.9 (2022-2023)
These versions continued to expand Swift’s capabilities in high-level and low-level domains. Swift 5.6 and 5.7 firmed up (?) concurrency by introducing the concept of Sendable and stricter compile-time checks to prevent data races (initially as warnings) across concurrency domains. They also introduced improvements like any keyword for existential types and refined generics. Swift 5.7/5.8 brought more generics features and improvements in Swift Package Manager and multiplatform support (including official Windows support). Swift 5.9 (mid-2023) introduced macro metaprogramming and experimental ownership control features.
* Macro metaprogramming is a compile-time system of user-defined macros that generate or transform code before it’s compiled, enabling boilerplate reduction and domain-specific language constructs. It’s like having a master chef who, at recipe-writing time, pre-chops your ingredients for you. So when you cook, you just follow the streamlined steps without tedious prep, letting you focus on the flavor instead of the grunt work.
For example, in a threat-detection system you could write a macro that, given a new IOC schema, auto-generates all the parsing and alert-rule boilerplate at compile time, so when a novel malware indicator format arrives, your engine instantly supports it without error-prone hand-coding.
Macros give developers compile-time code generation capabilities (e.g. to synthesize boilerplate or create domain-specific languages within Swift), indicating a shift to empower meta-programming while maintaining type safety. The ownership features (introduced as “non-copyable types” with the ~Copyable marker in Swift 5.9) allow developers to opt into move semantics for certain types, eliminating ARC overhead for those and enabling patterns like in-place mutation and unique ownership. These low-level features were driven by a philosophy of giving systems programmers more control when needed (a nod to languages like Rust) without abandoning Swift’s safety guarantees.
Swift 6.0 (2024)
Released in late 2024, Swift 6 focused on making concurrency safer by default and extending Swift’s reach. It introduced an opt-in strict concurrency checking mode that elevates potential data races to compile-time errors, effectively providing data-race freedom when enabled. This means Swift 6 can guarantee thread safety for code that adopts the new checks, a significant step in language-level safety.
Swift 6 also stabilized and expanded the ownership features from 5.9, allowing generic algorithms to work with move-only types and reduced unnecessary copying for performance-critical code. Other notable additions include typed throws (ability to specify exact error types a function can throw) for clearer error-handling contracts, and improvements to C++ interoperability (supporting C++ templates, std:: collections, etc., making Swift more practical in mixed-language projects). By this point, I’d say Swift’s design philosophy is fully matured (although I am not a developer): the language emphasizes safety and approachability for application development, yet “scales down” to systems-level programming with features like explicit memory ownership and concurrency control when needed. Swift 6 also continue expanding its platform range (with official support for embedded systems and Linux/Windows), reflecting a goal of making Swift a general-purpose language without losing its home in macOS/iOS app development.
Throughout all this history, Swift’s principles have remained safety, performance, and expressiveness.