# YJIT

> Shopify's just-in-time compiler for Ruby, merged in 3.1 and declared production-ready in 3.2.

- December 25, 2021: YJIT merged into Ruby 3.1 (experimental)
- December 25, 2022: YJIT declared production-ready in Ruby 3.2

**YJIT** is a just-in-time compiler for Ruby, built by a team at the e-commerce company Shopify to make Ruby programs run faster. A "JIT compiler" watches your program as it runs, notices the code paths that execute over and over, and translates just those hot spots into native machine code (the low-level instructions a processor runs directly) so they stop going through Ruby's slower general-purpose interpreter. Ruby 3.1 "merges YJIT, a new in-process JIT compiler developed by Shopify" on **December 25, 2021**, where it shipped as experimental and off by default, showing gains like 22% on a Rails benchmark.

One year later, in **Ruby 3.2** on December 25, 2022, YJIT was "no longer experimental," having "been tested on production workloads for over a year and proven to be quite stable." By then its internals were being written in the Rust programming language, so building it required a Rust compiler. YJIT was part of the long push for speed that also drove [Ruby 3.0](https://chunkybacon.dev/timeline/ruby-3-0.md)'s "Ruby 3x3" goal.

*Related:* [Ruby 3.0](https://chunkybacon.dev/timeline/ruby-3-0.md) · [Ruby 4.0](https://chunkybacon.dev/timeline/ruby-4-0.md) · [The Christmas-release tradition](https://chunkybacon.dev/stories/the-christmas-release-tradition.md)

## Sources
- Ruby 3.1.0 Released (official announcement, YJIT merged, Shopify): https://www.ruby-lang.org/en/news/2021/12/25/ruby-3-1-0-released/
- Ruby 3.2.0 Released (official announcement, YJIT no longer experimental, Rust build requirement): https://www.ruby-lang.org/en/news/2022/12/25/ruby-3-2-0-released/

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Source: https://chunkybacon.dev/timeline/yjit/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)