What new Swift concurrency properties have been added in Swift 6.2
Asked on 06/11/2025
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In Swift 6.2, several new concurrency properties and improvements have been introduced to make concurrency more approachable and safer. Here are some key changes:
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Single-threaded by Default: Swift 6.2 changes the default behavior to stay single-threaded until concurrency is explicitly introduced. This makes the most natural code data race-free by default, providing a safer path to introducing concurrency in projects.
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Async Functions on Mutable State: It is now easier to call async functions on types with mutable state. Instead of offloading async functions that aren't tied to a specific actor, the function will continue to run on the actor it was called from, eliminating data races.
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Isolated Conformances: Swift 6.2 supports isolated conformances, allowing conformances that need main actor state to be safely implemented. The compiler ensures that a main actor conformance is only used on the main actor.
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Concurrent Attribute: A new concurrent attribute allows for offloading CPU-intensive tasks to the background, keeping apps responsive.
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Opt-in Language Changes: Some concurrency language changes are opt-in and can be enabled under the Swift Compiler Concurrency section of Xcode Build Settings or in a Swift package manifest file using the Swift Settings API.
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Migration Tooling: Swift 6.2 includes migration tooling to help make necessary code changes automatically, making it easier to adopt these concurrency improvements.
For more detailed information, you can refer to the session What’s new in Swift (00:30:28).
What’s new in Swift
Join us for an update on Swift. We’ll talk about workflow improvements that make you more productive, and new and modernized library APIs for fundamental programming tasks. We’ll show examples of Swift adoption throughout more layers of the software stack. Finally, we’ll explore new language features for both improving approachability of concurrency, and achieving peak performance when you need it.
Platforms State of the Union
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What’s new in Swift
Join us for an update on Swift. We’ll briefly go through a history of Swift over the past decade, and show you how the community has grown through workgroups, expanded the package ecosystem, and increased platform support. We’ll introduce you to a new language mode that achieves data-race safety by default, and a language subset that lets you run Swift on highly constrained systems. We’ll also explore some language updates including noncopyable types, typed throws, and improved C++ interoperability.