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What is ABI stability? Why does it matter in Swift development?

ABI stability is an important concept in Swift development. ABI stands for application binary interface. ABI stability guarantees that applications compiled with different versions of the Swift compiler will be able to run on the same version of the Swift runtime (Rose, 2019). This means that developers can update the Swift compiler without having to recompile their apps. ABI stability also allows apps to be more easily portable to other platforms. Swift development would be much more difficult without ABI stability.

Swift 5.0 has been released, and it is now stable. This means that the code written in Swift can be used in all of Apple’s platforms: macOS, iOS, tvOS, and watchOS. On Swift’s official page (Geoff, 2019) ABI stability brings many benefits to developers and users of Swift:

  • The most apparent benefit of Swift being available in more platforms is that applications written in it no longer need to be distributed with the Swift runtime libraries, saving storage space.
  • With these host operating systems, the Swift runtime can be more deeply embedded and optimized, allowing Swift applications to launch faster, have better runtime performance, and use less memory.
  • In future operating systems, Apple will be able to use Swift to provide platform frameworks.
  • Third parties will be able to ship binary frameworks written in Swift when a future version of Swift also supports module stability.

ABI stability can makes programming in Swift more like programming in other languages, and less reliant on versioning tricks to maintain compatibility. Can you imagine, application developed on Swift can be used on multiple platforms? This is how my ARM M1 Mac can also download, install and utilize iOS apps. What do you think about that?


Geoff, (2019, February, 11). Evolving Swift On Apple Platforms After ABI Stability. Retrieved from

Rose, J. (2019). ABI Stability and More. Retrieved from