--- title: Kotlin Variance: Stop Confusing in & out | daily.dev description: A practical guide to understanding Kotlin variance using a mental model based on type flow direction. Covers covariance (out) for producers, contravariance... canonical: https://daily.dev/posts/kotlin-variance-stop-confusing-in-out-enrb55aty twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Kotlin Variance: Stop Confusing in & out | daily.dev og:description: A practical guide to understanding Kotlin variance using a mental model based on type flow direction. Covers covariance (out) for producers, contravariance... og:url: https://daily.dev/posts/kotlin-variance-stop-confusing-in-out-enrb55aty og:image: https://api.daily.dev/og/posts/eNrB55AtY.png og:image:alt: Kotlin Variance: Stop Confusing in & out 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. # Kotlin Variance: Stop Confusing in & out **[ProAndroidDev](https://daily.dev/sources/pand)** · 5 min read · 0 upvotes · 0 comments ## Summary A practical guide to understanding Kotlin variance using a mental model based on type flow direction. Covers covariance (out) for producers, contravariance (in) for consumers, and invariance for types that do both. Includes real-world examples from the Kotlin standard library (List, Comparator), use-site variance with type projections, and a cheat sheet for interview preparation. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Evaluating Kotlin in Real Projects](https://daily.dev/posts/evaluating-kotlin-in-real-projects-4hvtaptzn) · JetBrains · 4 upvotes · 0 comments - [Variables, Constants, and Data Types in Kotlin: A Beginner-Friendly Guide](https://daily.dev/posts/variables-constants-and-data-types-in-kotlin-a-beginner-friendly-guide-rkyab6sww) · Medium · 0 upvotes · 0 comments - [Kotlin Flows in Android: A Clear Mental Model](https://daily.dev/posts/kotlin-flows-in-android-a-clear-mental-model-ln8rffwwm) · Medium · 0 upvotes · 0 comments --- Tags: [#android](https://daily.dev/tags/android), [#kotlin](https://daily.dev/tags/kotlin) [View this post on daily.dev](https://daily.dev/posts/kotlin-variance-stop-confusing-in-out-enrb55aty) ```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":"Kotlin Variance: Stop Confusing in & out","url":"https://daily.dev/posts/kotlin-variance-stop-confusing-in-out-enrb55aty","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/kotlin-variance-stop-confusing-in-out-enrb55aty"},"datePublished":"2026-03-01T06:41:29.579Z","dateModified":"2026-03-01T06:41:49.834Z","description":"A practical guide to understanding Kotlin variance using a mental model based on type flow direction. 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