--- title: You Don't Need an Iframe Resizing Library | daily.dev description: A walkthrough of building a lightweight iframe auto-resizing solution using the Window.postMessage API and ResizeObserver, avoiding the need for third-party... canonical: https://daily.dev/posts/you-don-t-need-an-iframe-resizing-library-o16fzclg5 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: You Don't Need an Iframe Resizing Library | daily.dev og:description: A walkthrough of building a lightweight iframe auto-resizing solution using the Window.postMessage API and ResizeObserver, avoiding the need for third-party... og:url: https://daily.dev/posts/you-don-t-need-an-iframe-resizing-library-o16fzclg5 og:image: https://api.daily.dev/og/posts/o16fzclg5.png og:image:alt: You Don't Need an Iframe Resizing Library 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. # You Don't Need an Iframe Resizing Library **[Svix Blog](https://daily.dev/sources/svix)** · 6 min read · 0 upvotes · 0 comments ## Summary A walkthrough of building a lightweight iframe auto-resizing solution using the Window.postMessage API and ResizeObserver, avoiding the need for third-party iframe-resizer libraries. The child page observes its content size and posts height updates to the parent, which listens for messages and adjusts the iframe's height. The approach can be extended to handle loading states or error reporting, and is used in production for Svix's embedded Consumer Application Portal in the svix-react library. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How can I make an iframe automatically resize to fit its content without using a library? Use the ResizeObserver API inside the iframe's child page to detect content size changes, then send the height to the parent page via window.parent.postMessage. The parent listens for the message with window.addEventListener('message', ...), verifies the event.source matches the iframe's contentWindow, and sets the iframe's style.height accordingly. _daily.dev surfaces practical browser API patterns like this for developers building embeddable widgets._ ### Why avoid third-party iframe resizing libraries in a React app? Popular iframe resizing libraries tend to be complex and bloated because they support many edge cases, some lack an MIT license, and they can be hard to customize when you need slightly different behavior. A custom implementation using postMessage and ResizeObserver can fit in a few dozen lines of code with no external dependencies and is easier to adapt to specific needs. _Developers weighing build-vs-buy on small utilities can find similar trade-off discussions on daily.dev._ ## Similar posts on daily.dev - [New in Chrome 154: iframes that automatically resize themselves to their content](https://daily.dev/posts/new-in-chrome-154-iframes-that-automatically-resize-themselves-to-their-content-tg1hez2ee) · Bram.us · 19 upvotes · 2 comments - [Transitioning Field Sizing Content With CSS · October 3, 2026](https://daily.dev/posts/transitioning-field-sizing-content-with-css-october-3-2026-gbbw5edae) · Adam Argyle · 2 upvotes · 0 comments - [Stop using JavaScript to solve CSS problems](https://daily.dev/posts/stop-using-javascript-to-solve-css-problems-utawse2td) · LogRocket · 208 upvotes · 8 comments --- Tags: [#javascript](https://daily.dev/tags/javascript), [#react](https://daily.dev/tags/react) [View this post on daily.dev](https://daily.dev/posts/you-don-t-need-an-iframe-resizing-library-o16fzclg5) ```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":"You Don't Need an Iframe Resizing Library","url":"https://daily.dev/posts/you-don-t-need-an-iframe-resizing-library-o16fzclg5","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/you-don-t-need-an-iframe-resizing-library-o16fzclg5"},"datePublished":"2026-08-23T07:20:27.258Z","dateModified":"2026-08-23T07:23:44.685Z","description":"A walkthrough of building a lightweight iframe auto-resizing solution using the Window.postMessage API and ResizeObserver, avoiding the need for third-party...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/58f98a2d3a32e2618e34ea1a1ec4564c?_a=AQAEuop","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/58f98a2d3a32e2618e34ea1a1ec4564c?_a=AQAEuop","isAccessibleForFree":true,"articleSection":"Svix 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":"Svix Blog","logo":"https://media.daily.dev/image/upload/s--Shf9MlOr--/f_auto,q_auto/v1787469609/logos/svix?_a=BAMAMicg0","url":"https://daily.dev/sources/svix"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/you-don-t-need-an-iframe-resizing-library-o16fzclg5","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"javascript,react","timeRequired":"PT6M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Svix Blog","item":"https://daily.dev/sources/svix"},{"@type":"ListItem","position":3,"name":"You Don't Need an Iframe Resizing Library"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/you-don-t-need-an-iframe-resizing-library-o16fzclg5#faq","mainEntity":[{"@type":"Question","name":"How can I make an iframe automatically resize to fit its content without using a library?","acceptedAnswer":{"@type":"Answer","text":"Use the ResizeObserver API inside the iframe's child page to detect content size changes, then send the height to the parent page via window.parent.postMessage. 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