--- title: Writing Custom Renderers for React | daily.dev description: A deep dive into how React renderers work, written by the maintainer of React Native Testing Library (RNTL) who built a new custom test renderer after React... canonical: https://daily.dev/posts/writing-custom-renderers-for-react-tp0cc3d7x twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Writing Custom Renderers for React | daily.dev og:description: A deep dive into how React renderers work, written by the maintainer of React Native Testing Library (RNTL) who built a new custom test renderer after React... og:url: https://daily.dev/posts/writing-custom-renderers-for-react-tp0cc3d7x og:image: https://api.daily.dev/og/posts/tp0CC3D7X.png og:image:alt: Writing Custom Renderers for React 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. # Writing Custom Renderers for React **[Callstack Blog](https://daily.dev/sources/callstack-blog)** · 10 min read · 11 upvotes · 0 comments ## Summary A deep dive into how React renderers work, written by the maintainer of React Native Testing Library (RNTL) who built a new custom test renderer after React Test Renderer was deprecated in React 19. Covers the three core trees React uses (element tree, Fiber tree, host instance tree), the two-phase reconciler process (rendering and committing), the HostConfig interface renderers must implement, and the difference between mutation and persistence renderer modes. Includes concrete code examples of host instance types and operations, plus lessons learned about tight coupling between React, Reconciler, and renderer versions. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [React Behind The Scenes: Virtual DOM, Reconciliation, Render Phase, Commit Phase & Fiber Explained.](https://daily.dev/posts/react-behind-the-scenes-virtual-dom-reconciliation-render-phase-commit-phase-fiber-explained--9uynk7eyd) · Medium · 5 upvotes · 0 comments --- Tags: [#react](https://daily.dev/tags/react), [#testing](https://daily.dev/tags/testing), [#react-native](https://daily.dev/tags/react-native) [View this post on daily.dev](https://daily.dev/posts/writing-custom-renderers-for-react-tp0cc3d7x) ```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":"Writing Custom Renderers for React","url":"https://daily.dev/posts/writing-custom-renderers-for-react-tp0cc3d7x","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/writing-custom-renderers-for-react-tp0cc3d7x"},"datePublished":"2026-06-24T08:50:11.370Z","dateModified":"2026-06-24T18:20:12.153Z","description":"A deep dive into how React renderers work, written by the maintainer of React Native Testing Library (RNTL) who built a new custom test renderer after React...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/1fb9cd586c11cb031993043983de7c82?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/1fb9cd586c11cb031993043983de7c82?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Callstack Blog","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":"Callstack Blog","logo":"https://media.daily.dev/image/upload/s--3qItoroi--/f_auto,q_auto/v1774179048/logos/callstack-blog?_a=BAMAMiWQ0","url":"https://daily.dev/sources/callstack-blog"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/writing-custom-renderers-for-react-tp0cc3d7x","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":11},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"react,testing,react-native","timeRequired":"PT10M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Callstack Blog","item":"https://daily.dev/sources/callstack-blog"},{"@type":"ListItem","position":3,"name":"Writing Custom Renderers for React"}]} ```