--- title: Where Does Your Swift async Code Actually Run? | daily.dev description: A hands-on investigation into where Swift async code actually executes, using thread logging across ten concurrency experiments. The key insight: async does... canonical: https://daily.dev/posts/where-does-your-swift-async-code-actually-run--hyeoiirp4 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Where Does Your Swift async Code Actually Run? | daily.dev og:description: A hands-on investigation into where Swift async code actually executes, using thread logging across ten concurrency experiments. The key insight: async does... og:url: https://daily.dev/posts/where-does-your-swift-async-code-actually-run--hyeoiirp4 og:image: https://api.daily.dev/og/posts/HYEoIiRP4.png og:image:alt: Where Does Your Swift async Code Actually Run? og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Where Does Your Swift async Code Actually Run? **[Medium](https://daily.dev/sources/medium_js)** · 7 min read · 0 upvotes · 0 comments ## Summary A hands-on investigation into where Swift async code actually executes, using thread logging across ten concurrency experiments. The key insight: async does not mean background thread — isolation determines the thread, not the async keyword. Swift 6.2 (SE-0461) reversed the previous default so nonisolated async functions now run on the caller's actor instead of hopping to the global executor. The new @concurrent attribute explicitly requests background execution. Also covered: how bare Task {} outlives views and can cause memory leaks, versus SwiftUI's .task {} modifier which cancels automatically on view dismissal. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Swift Concurrency is Gaining Broader Adoption -- Fatbobman's Swift Weekly \#133](https://daily.dev/posts/swift-concurrency-is-gaining-broader-adoption----fatbobman-s-swift-weekly-133-40hcoackj) · Fatbobman · 0 upvotes · 0 comments - [Approachable Concurrency in Swift 6.2: A Clear Guide](https://daily.dev/posts/approachable-concurrency-in-swift-6-2-a-clear-guide-srya8fign) · SwiftLee · 1 upvotes · 0 comments - [Fucking Approachable Swift Concurrency](https://daily.dev/posts/fucking-approachable-swift-concurrency-dmob6pupx) · Hacker News · 0 upvotes · 0 comments --- Tags: [#swift](https://daily.dev/tags/swift), [#swiftui](https://daily.dev/tags/swiftui) [View this post on daily.dev](https://daily.dev/posts/where-does-your-swift-async-code-actually-run--hyeoiirp4) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Where Does Your Swift async Code Actually Run?","url":"https://daily.dev/posts/where-does-your-swift-async-code-actually-run--hyeoiirp4","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/where-does-your-swift-async-code-actually-run--hyeoiirp4"},"datePublished":"2026-07-18T20:42:16.410Z","dateModified":"2026-07-18T20:44:12.423Z","description":"A hands-on investigation into where Swift async code actually executes, using thread logging across ten concurrency experiments. 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