# Embedded Swift Improvements Coming in Swift 6.4

DevFeed: [Embedded Swift Improvements Coming in Swift 6.4](<https://devfeed.tech/articles/embedded-swift-improvements-coming-in-swift-6-4-2929.md>)

Original publisher: [Read original article](<https://swift.org/blog/embedded-swift-improvements-coming-in-swift-6.4/>)

Author: Doug Gregor

Published: 2026-08-20T13:45:00Z

Content type: article

Language: en

Sources: [Swift.org](<https://devfeed.tech/sources/swift-org.md>)

Topics: [Swift](<https://devfeed.tech/topics/swift.md>), [Code](<https://devfeed.tech/topics/code.md>)

Tags: [code](<https://devfeed.tech/tags/code.md>), [development](<https://devfeed.tech/tags/development.md>), [embedded](<https://devfeed.tech/tags/embedded.md>), [features](<https://devfeed.tech/tags/features.md>), [performance](<https://devfeed.tech/tags/performance.md>), [post](<https://devfeed.tech/tags/post.md>), [release](<https://devfeed.tech/tags/release.md>), [swift](<https://devfeed.tech/tags/swift.md>)

## AI overview

This article describes improvements coming to Embedded Swift in Swift 6.4, including broader language compatibility, generalized existential type support, and untyped throws. It also discusses the effects of dynamic features on runtime performance and code size.

## Source excerpt

Embedded Swift is a subset of Swift that's designed for low resource usage, making it capable of running on constrained environments like microcontrollers. Using a special compilation mode, Embedded Swift produces significantly smaller binaries than regular Swift. While a subset of the full language, the vast majority of the Swift language works exactly the same in Embedded Swift. Additional information is described in the Embedded Swift vision document. Embedded Swift is evolving rapidly. Following our updates on Embedded Swift improvements in Swift 6.3 late last year, this post describes a number of additional improvements made in the upcoming Swift 6.4 release. You can try them out today with a Swift development snapshot. Language improvements Embedded Swift continues to expand its subset of the language to include more aspects of "full" Swift, making it easier than ever to bring compatibility with Embedded Swift to existing Swift code bases. Many of these features have some dynamic aspect to them, meaning that they have an impact on runtime performance (for example, due to indirect calls) and code size (due to requiring additional metadata). However, this impact only occurs where these dynamic language features are actually used: code that is highly sensitive to code size and performance can choose to avoid them, for example by enabling warnings in the PerformanceHints diagnostic group. Generalized support for existential (any) types any) types section" href="#generalized-support-for-existential-any-types"> Embedded Swift previously only supported existential (any) types that had an AnyObject constraint, meaning they could only be used with class instances. Now, all any types are available in Embedded Swift, including Any itself. For example: protocol P { func method() } extension Int: P { func method() { print("\(self) is here") } } let a: any P = 17 a.method() // prints "17 is here" The Embedded Swift generics compilation model, which requires that all generic