--- title: 🦀 Rust Inside Ruby Core: A New Systems Layer for MRI description: Parts of CRuby (MRI) are now written in Rust, specifically in the YJIT just-in-time compiler introduced in Ruby 3.1. YJIT compiles Ruby bytecode into native... canonical: https://daily.dev/posts/rust-inside-ruby-core-a-new-systems-layer-for-mri-dfgkrj66q twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: 🦀 Rust Inside Ruby Core: A New Systems Layer for MRI | daily.dev og:description: Parts of CRuby (MRI) are now written in Rust, specifically in the YJIT just-in-time compiler introduced in Ruby 3.1. YJIT compiles Ruby bytecode into native... og:url: https://daily.dev/posts/rust-inside-ruby-core-a-new-systems-layer-for-mri-dfgkrj66q og:image: https://api.daily.dev/og/posts/dfGkrj66Q.png og:image:alt: 🦀 Rust Inside Ruby Core: A New Systems Layer for MRI og:image:width: 1200 og:image:height: 630 og:locale: en --- [Ruby Flow](https://daily.dev/sources/rubyflow) [Read post](https://api.daily.dev/r/dfGkrj66Q) # [🦀 Rust Inside Ruby Core: A New Systems Layer for MRI](https://api.daily.dev/r/dfGkrj66Q "Go to post") Parts of CRuby (MRI) are now written in Rust, specifically in the YJIT just-in-time compiler introduced in Ruby 3.1\. YJIT compiles Ruby bytecode into native machine code at runtime and is implemented largely in Rust, which provides low-level control with memory safety guarantees C cannot offer. The rest of the Ruby runtime — interpreter, parser, GC, object model, standard library — remains in C. This hybrid C/Rust architecture is a strategic addition, not a rewrite, targeting only the most complex and risk-sensitive subsystem. The move signals that the Ruby core team is open to modern systems languages and prioritizes memory safety in performance-critical components, mirroring similar selective Rust adoption in Linux, Android, and database engines. [#rust](/tags/rust "Check all #rust posts")[#ruby](/tags/ruby "Check all #ruby posts") Feb 28 • 4m read time • From [rubystacknews.com](https://api.daily.dev/r/dfGkrj66Q "rubystacknews.com") [](https://api.daily.dev/r/dfGkrj66Q "Go to post") Table of contents [Where Rust Is Actually Used: YJIT](https://api.daily.dev/r/dfGkrj66Q "Where Rust Is Actually Used: YJIT")[ Why This Component?](https://api.daily.dev/r/dfGkrj66Q "Why This Component?")[ A Glimpse of Rust Code in Ruby Core](https://api.daily.dev/r/dfGkrj66Q "A Glimpse of Rust Code in Ruby Core")[ How Rust Integrates with the C Runtime](https://api.daily.dev/r/dfGkrj66Q "How Rust Integrates with the C Runtime")[ Why This Matters](https://api.daily.dev/r/dfGkrj66Q "Why This Matters")[ Not a Rewrite — A Strategic Addition](https://api.daily.dev/r/dfGkrj66Q "Not a Rewrite — A Strategic Addition")[ A Quiet but Meaningful Shift](https://api.daily.dev/r/dfGkrj66Q "A Quiet but Meaningful Shift")[ Final Thoughts](https://api.daily.dev/r/dfGkrj66Q "Final Thoughts")[ Share this:](https://api.daily.dev/r/dfGkrj66Q "Share this:")[ Related](https://api.daily.dev/r/dfGkrj66Q "Related") Comment Bookmark Copy Share your thoughts Post Share this post [](https://daily.dev/sources/rubyflow) [Ruby Flow](https://daily.dev/sources/rubyflow "https://daily.dev/sources/rubyflow") RubyFlow's platform is a resource for Ruby developers, offering insights into Ruby programming langu... 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