--- title: Box2D 3.1 :: Box2D | daily.dev description: Box2D 3.1 refines the major 3.0 release with bug fixes and new features. Highlights include an experimental geometric character mover for finer movement... canonical: https://daily.dev/posts/box2d-3-1-box2d-4d5ioknrp twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Box2D 3.1 :: Box2D | daily.dev og:description: Box2D 3.1 refines the major 3.0 release with bug fixes and new features. Highlights include an experimental geometric character mover for finer movement... og:url: https://daily.dev/posts/box2d-3-1-box2d-4d5ioknrp og:image: https://api.daily.dev/og/posts/4d5IOKNrP.png og:image:alt: Box2D 3.1 :: Box2D 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. # Box2D 3.1 :: Box2D **[ Box2D ](https://daily.dev/sources/box2d)** · 3 min read · 0 upvotes · 0 comments ## Summary Box2D 3.1 refines the major 3.0 release with bug fixes and new features. Highlights include an experimental geometric character mover for finer movement control, a rebuilt sensor system that runs at the end of the update loop for reliable, deterministic, multithreaded overlap events, and new surface properties (rolling resistance and tangent speed) using the SIMD contact solver. SSE2 is now the default SIMD path on x64 since not all CPUs support AVX2, Neon was optimized for Apple Silicon, and continuous collision performance roughly doubled while GJK got 20% faster. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What's new in Box2D 3.1 compared to 3.0? Box2D 3.1 adds an experimental geometric character mover, a rebuilt sensor system that runs at the end of the update loop for reliable deterministic overlap events, rolling resistance and tangent speed surface properties, and performance improvements including roughly doubled continuous collision performance and a 20% faster GJK algorithm. _Track new Box2D releases like this on daily.dev to keep physics-based game code current._ ### Why did Box2D switch its default SIMD instruction set from AVX2 to SSE2 on x64? Not every x64 CPU supports AVX2, so Box2D 3.1 made SSE2 the default SIMD path on x64 for broader compatibility, while still allowing SIMD to be disabled entirely for slower fallback execution. Neon SIMD was also optimized, yielding significant gains on Apple Silicon. _Developers tuning cross-platform physics performance can follow SIMD changes like this on daily.dev._ ### How does the new sensor system in Box2D 3.1 differ from the old one? The previous sensor system was built on the contact system, which caused delayed overlap events and coupled sensor behavior to body type and sleep status. Box2D 3.1's new sensor system runs at the end of the update, ignores body type and sleeping status, and produces reliable, multithreaded, deterministic begin and end touch events with access to current overlaps. _Game developers evaluating physics engine internals can follow updates like this on daily.dev._ ## Similar posts on daily.dev - [SIMD for Collision :: Box2D](https://daily.dev/posts/simd-for-collision-box2d-wsosdjqbv) · Lobsters · 0 upvotes · 0 comments - [Box3D Debuts As New Open-Source 3D Physics Engine](https://daily.dev/posts/box3d-debuts-as-new-open-source-3d-physics-engine-xsk1j9ymw) · Phoronix · 0 upvotes · 0 comments - [Announcing Box3D :: Box2D](https://daily.dev/posts/announcing-box3d-box2d-mu8ehdvki) · Lobsters · 0 upvotes · 0 comments --- Tags: [#performance](https://daily.dev/tags/performance), [#game-development](https://daily.dev/tags/game-development) [View this post on daily.dev](https://daily.dev/posts/box2d-3-1-box2d-4d5ioknrp) ```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":"Box2D 3.1 :: Box2D","url":"https://daily.dev/posts/box2d-3-1-box2d-4d5ioknrp","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/box2d-3-1-box2d-4d5ioknrp"},"datePublished":"2026-08-23T12:16:49.349Z","dateModified":"2026-08-23T12:19:50.138Z","description":"Box2D 3.1 refines the major 3.0 release with bug fixes and new features. 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