--- title: This Month in Ladybird | daily.dev description: December's development recap for the Ladybird browser covers 197 merged PRs from 37 contributors. Highlights include new sponsors (FUTO renewing at $250,000,... canonical: https://daily.dev/posts/this-month-in-ladybird-golvfvcm4 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: This Month in Ladybird | daily.dev og:description: December's development recap for the Ladybird browser covers 197 merged PRs from 37 contributors. Highlights include new sponsors (FUTO renewing at $250,000,... og:url: https://daily.dev/posts/this-month-in-ladybird-golvfvcm4 og:image: https://api.daily.dev/og/posts/gOlvFVCm4.png og:image:alt: This Month in Ladybird 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. # This Month in Ladybird **[Ladybird Browser](https://daily.dev/sources/ladybird)** · 5 min read · 0 upvotes · 0 comments ## Summary December's development recap for the Ladybird browser covers 197 merged PRs from 37 contributors. Highlights include new sponsors (FUTO renewing at $250,000, plus smaller sponsorships), progress on Web Platform Tests, CSS features like ::part() pseudo-element and the random() function, media playback improvements for streaming and mixed sample rates, several JavaScript engine performance optimizations, HTTP disk caching enabled by default with stale-while-revalidate support, garbage collector leak fixes that reduced leaked Window objects from ~240 to ~25, and early work on post-quantum cryptography (ML-DSA, ML-KEM) plus SHA-3 and Argon2 in the Web Cryptography API. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### Does Ladybird support the CSS ::part() pseudo-element for styling shadow DOM parts of custom elements? Yes, Ladybird added basic support for the ::part() pseudo-element, which lets custom elements expose parts of their shadow DOM for external styling, such as widget::part(quantity) targeting elements with part="quantity" inside widget's shadow DOM. The exportparts attribute is not yet implemented, but the feature already improves rendering on sites like MDN. _Track browser engine feature rollouts like this one as you plan CSS support on daily.dev._ ### Does Ladybird enable HTTP disk caching by default and support stale-while-revalidate? Yes, Ladybird enabled the HTTP disk cache by default, cutting redundant network traffic on repeat visits, and implemented the stale-while-revalidate Cache-Control directive, which serves a stale cached response immediately while revalidating with the origin server in the background. _Developers tuning cache-control headers can follow browser caching behavior changes on daily.dev._ ### What caused garbage collector leaks in the Ladybird browser engine and how were they fixed? Leaks stemmed mainly from improper use of GC::Root, which stored strong references that kept objects alive forever in places like 2D canvas fill/stroke styles, the rejected promises list, the custom elements reaction stack, BroadcastChannel, and IndexedDB. Switching most of these to GC::Weak references, plus introducing a new GC::HeapVector container, reduced leaked Window objects in a full test-web run from about 240 to about 25. _Engineers debugging GC leaks in browser or runtime internals can follow fixes like this on daily.dev._ --- Tags: [#css](https://daily.dev/tags/css) [View this post on daily.dev](https://daily.dev/posts/this-month-in-ladybird-golvfvcm4) ```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":"This Month in Ladybird","url":"https://daily.dev/posts/this-month-in-ladybird-golvfvcm4","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/this-month-in-ladybird-golvfvcm4"},"datePublished":"2026-08-31T05:54:44.000Z","dateModified":"2026-08-31T05:56:28.317Z","description":"December's development recap for the Ladybird browser covers 197 merged PRs from 37 contributors. 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