21CTO

Jan 7, 2026 · Fundamentals

What’s New in Ruby 4.0? Exploring Box Isolation, ZJIT, and Ractor Enhancements

Ruby 4.0, released on December 25 to mark the language’s 30th anniversary, introduces experimental Box isolation, the ZJIT compiler, and a revamped Ractor for concurrency, but many features remain immature and optional for production use.