ZJIT

ZJIT is a method-based just-in-time (JIT) compiler for Ruby. Check out the source and docs.

What people are saying

Here are some blog posts and talks about ZJIT.

Blog posts

• ZJIT 🤝 GC: Inlining GC Fastpath in ZJIT 1 Sep 2026
• The inliner is yielding benefits for ZJIT 28 Jul 2026
• A new Register Allocator for ZJIT 27 May 2026
• Using Perfetto in ZJIT 27 Mar 2026
• How ZJIT removes redundant object loads and stores 18 Mar 2026
• A multi-entry CFG design conundrum 22 Jan 2026
• ZJIT is now available in Ruby 4.0 24 Dec 2025
• How to annotate JITed code for perf/samply 18 Dec 2025
• Adding Iongraph support to ZJIT 19 Nov 2025
• How Ruby Executes JIT Code 8 Sep 2025
• ZJIT has been merged into Ruby 14 May 2025

Talks

• RubyKaigi 2026 (videos and slides coming soon)
  • The design and implementation of ZJIT & the next five years
  • A Faster FFI
  • Whose Memory is it Anyway
  • Lightning-Fast Method Calls with Ruby 4.1 ZJIT
• REBASE 2025 video slides
• SFRuby 2025 video slides
• RubyKaigi 2025 video slides

Papers

• Support Local Variables
  Maxwell Bernstein, Takashi Kokubun, Kevin Menard, Aaron Patterson, Si Xing (Alan) Wu
  in VMIL 2026
  [PDF] [ARX]