ZJIT
Ranked 5 of 6 JIT compilers by recommenders
Ruby's experimental JIT compiler, free with Ruby 4.0, valued for its performance work and ongoing investment. Core team advises against production use for now.
Ruby's experimental JIT compiler, free with Ruby 4.0, valued for its performance work and ongoing investment. Core team advises against production use for now.
9 people gave an opinion
- recommend it
- 7
- criticize it
- 2
- approval share
- 78%
Recommended in 5 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: not recommended
- February 2026: not recommended
- March 2026: recommended
- April 2026: not recommended
- May 2026: recommended
- June 2026: not recommended
- July 2026: not recommended
- August 2026: not recommended
- September 2026: not recommended
- October 2026: recommended
- November 2026: not recommended (month in progress)
Why it doesn’t carry the badge
- 7 people recommend itNeeds 10 or more, not met.
- 3.5 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 5 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Ongoing investment in Ruby JITs
“significant investment recently in JITs, in particular YJIT and ZJIT”
Comment from 9 Nov 2025 in “Friendly attributes pattern in Ruby” “having ZJIT and production ready Ractors is really good”
Comment from 18 Dec 2025 in “What's New in Ruby 4.0” Replaces YJIT as Ruby's JIT
“luckily enough we now have ZJIT replacing YJIT”
Comment from 27 Oct 2026 in “Python's experimental JIT to be removed” “The current experimental JIT is ZJIT.”
Comment from 21 Dec 2025 in “Ruby website redesigned”
What people warn about
Each mark is one comment
Core team advises against production use
“even the core team recommends against using them in production for now”
Comment from 25 Dec 2025 in “Ruby 4.0.0 Released”
Other JIT compilers people recommend
The four most recommended other JIT compilers, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| Numba | 30 | 9 | 77% | 9 | — | Approved |
| CPython experimental JIT | 13 | 16 | 45% | 3 | — | — |
| YJIT | 10 | 2 | 83% | 6 | — | Approved |
| HotSpot JVM | 8 | 0 | 100% | 4 | — | — |
| ZJITThis page | 7 | 2 | 78% | 5 | — | — |
What people said
10 of the 11 comments that mention it, newest first. Each links to the original comment.
“luckily enough we now have ZJIT replacing YJIT”
“The escape analysis piece is what makes this particularly interesting.”
“Feels like javascript-esque runtime churn”
“It’s serious, professional engineering, and definitely deserves respect.”
“even the core team recommends against using them in production for now”
“The current experimental JIT is ZJIT.”
“having ZJIT and production ready Ractors is really good”
“they came up with a much simplier tier 0 method jit, which will never be able to surpass Maxime's yjit”
“I'm happy to get any free performance improvements!”
“significant investment recently in JITs, in particular YJIT and ZJIT”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.