Ruby 4.0.0 Released

kept by eddie dec 26, 25

Ruby 4.0.0 introduces experimental Ruby Box for isolated definitions and ZJIT, a new JIT compiler built in Rust, alongside Ractor improvements and core class updates.

What's new in Ruby 4.0
Ruby 4.0 ships Christmas 2025 with a new ZJIT compiler, redesigned Ractor ports, experimental isolated namespaces via Ruby::Box, and faster object allocations.
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