--- title: A Practical Guide to Isolate.run() in Flutter | daily.dev description: Flutter apps can feel unresponsive not because of widget rebuilds or state management, but because CPU-intensive work like JSON parsing, image processing, or... canonical: https://daily.dev/posts/a-practical-guide-to-isolate-run-in-flutter-y5cukzif9 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: A Practical Guide to Isolate.run() in Flutter | daily.dev og:description: Flutter apps can feel unresponsive not because of widget rebuilds or state management, but because CPU-intensive work like JSON parsing, image processing, or... og:url: https://daily.dev/posts/a-practical-guide-to-isolate-run-in-flutter-y5cukzif9 og:image: https://api.daily.dev/og/posts/y5CukzIf9.png og:image:alt: A Practical Guide to Isolate.run() in Flutter 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. # A Practical Guide to Isolate.run() in Flutter **[Medium](https://daily.dev/sources/medium_js)** · 5 min read · 1 upvotes · 0 comments ## Summary Flutter apps can feel unresponsive not because of widget rebuilds or state management, but because CPU-intensive work like JSON parsing, image processing, or encryption runs on the main UI isolate. Isolate.run() offloads that computation to a separate isolate, keeping the UI smooth. The key distinction is CPU-bound work (parsing, compressing, encrypting) versus I/O-bound work (network requests, database queries) — isolates help with the former but add unnecessary overhead to the latter. Spawning an isolate has a cost, so it's only worthwhile when the computation itself is heavy enough to justify it. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Isolates in Dart: True Parallelism Without Shared Memory](https://daily.dev/posts/isolates-in-dart-true-parallelism-without-shared-memory-rnvncclzj) · Medium · 0 upvotes · 0 comments - [The Cooperative Multitasking Trap: Why Asynchronous Loops Starve Mobile Runtimes](https://daily.dev/posts/the-cooperative-multitasking-trap-why-asynchronous-loops-starve-mobile-runtimes-9dpkv37dl) · ProAndroidDev · 0 upvotes · 0 comments --- Tags: [#performance](https://daily.dev/tags/performance), [#flutter](https://daily.dev/tags/flutter), [#dart](https://daily.dev/tags/dart) [View this post on daily.dev](https://daily.dev/posts/a-practical-guide-to-isolate-run-in-flutter-y5cukzif9) ```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":"A Practical Guide to Isolate.run() in Flutter","url":"https://daily.dev/posts/a-practical-guide-to-isolate-run-in-flutter-y5cukzif9","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/a-practical-guide-to-isolate-run-in-flutter-y5cukzif9"},"datePublished":"2026-07-20T20:07:33.522Z","dateModified":"2026-07-20T20:08:25.037Z","description":"Flutter apps can feel unresponsive not because of widget rebuilds or state management, but because CPU-intensive work like JSON parsing, image processing, or...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/ee16180a362977b0c32e243722635c4b?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/ee16180a362977b0c32e243722635c4b?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Medium","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Medium","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/medium","url":"https://daily.dev/sources/medium_js"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/a-practical-guide-to-isolate-run-in-flutter-y5cukzif9","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"performance,flutter,dart","timeRequired":"PT5M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Medium","item":"https://daily.dev/sources/medium_js"},{"@type":"ListItem","position":3,"name":"A Practical Guide to Isolate.run() in Flutter"}]} ```