https://www.ruby-lang.org/en/news/2025/11/17/ruby-4-0-0-preview2-released/

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Ruby 4.0.0 preview2 Released

Posted by naruse on 17 Nov 2025

We are pleased to announce the release of Ruby 4.0.0-preview2. Ruby
4.0 updates its Unicode version to 17,0.0, and so on.

Language changes

  * *nil no longer calls nil.to_a, similar to how **nil does not call
    nil.to_hash. [[Feature #21047]]

Core classes updates

Note: We're only listing notable updates of Core class.

  * Binding

      + Binding#local_variables does no longer include numbered
        parameters. Also, Binding#local_variable_get and Binding#
        local_variable_set reject to handle numbered parameters.
        [[Bug #21049]]
  * IO

      + IO.select accepts +Float::INFINITY+ as a timeout argument.
        [[Feature #20610]]
  * String

      + Update Unicode to Version 17.0.0 and Emoji Version 17.0.
        [[Feature #19908]][[Feature #20724]][[Feature #21275]] (also
        applies to Regexp)

Standard Library updates

Note: We're only listing notable updates of Standard librarires.

  * ostruct 0.6.1
  * pstore 0.2.0
  * benchmark 0.4.0
  * logger 1.7.0
  * rdoc 6.13.1
  * win32ole 1.9.2
  * irb 1.15.2
  * reline 0.6.1
  * readline 0.0.4
  * fiddle 1.1.6

Compatibility issues

Note: Excluding feature bug fixes.

Standard library compatibility issues

C API updates

JIT

  * YJIT
      + YJIT stats
          o ratio_in_yjit no longer works in the default build. Use
            --enable-yjit=stats on configure to enable it on
            --yjit-stats.
          o Add invalidate_everything to default stats, which is
            incremented when every code is invalidated by TracePoint.
      + Add mem_size: and call_threshold: options to
        RubyVM::YJIT.enable.
  * ZJIT
      + Add an experimental method-based JIT compiler. Use
        --enable-zjit on configure to enable the --zjit support.
      + As of Ruby 4.0.0-preview2, ZJIT is not yet ready for speeding
        up most benchmarks. Please refrain from evaluating ZJIT just
        yet. Stay tuned for the Ruby 4.0 release.
  * RJIT
      + --rjit is removed. We will move the implementation of the
        third-party JIT API to the ruby/rjit repository.

Miscellaneous changes

See NEWS or commit logs for more details.

With those changes, 3607 files changed, 197451 insertions(+), 285607
deletions(-) since Ruby 3.4.0!

Download

  * https://cache.ruby-lang.org/pub/ruby/4.0/
    ruby-4.0.0-preview2.tar.gz

    SIZE: 23444451
    SHA1: 132e450bbee3f61ed0b463ed1e2bd3a3a324339c
    SHA256: 0a3330dae710302e11f7f0323e83219ab3c6517984691a312c662f329c5120e1
    SHA512: b5e681cc84be59148485b9a2212dcf54d61cfee27431ceddb49bedc8baa913ec8b36da43242cb4f1791b25e4bfc1dcf72b5527288a0656f2933da898d0e0b40f

  * https://cache.ruby-lang.org/pub/ruby/4.0/
    ruby-4.0.0-preview2.tar.xz

    SIZE: 17554228
    SHA1: f8e8b98ea85ac82610ab601a21dc9a90c5c56a97
    SHA256: 0b92b15466d77a9d7e59e4a75f050d42cd50fe96c951d2b3b9f8029394cd9a43
    SHA512: 7afaa8d8e832ef0ded28f1caf874da69f16105e1b3aad5947c6911364159b4c6ebd3d7ea5d7d86708e9f2f06a047921b8302ca6e75ec429a3da846845f896976

  * https://cache.ruby-lang.org/pub/ruby/4.0/ruby-4.0.0-preview2.zip

    SIZE: 28933540
    SHA1: 48a235cfbfd4252dce81da870c792e32309e62b9
    SHA256: f5c68ee44dfcb76b61c07c437fa945814dfc516570b1c921506ac886960160ca
    SHA512: 508c685e46a641c74e2968daf650559503ce2bcaac3403654713adb2345c3ede2bace929294a1367afecac5edd6b2c42fa833f5313456f78c79151d310c860cf

What is Ruby

Ruby was first developed by Matz (Yukihiro Matsumoto) in 1993, and is
now developed as Open Source. It runs on multiple platforms and is
used all over the world especially for web development.

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