CPython experimental JIT
Ranked 2 of 6 JIT compilers by recommenders
Opt-in JIT compiler in CPython 3.15 that some people credit with real speedups, mostly on toy benchmarks. Critics say the gains are too small to justify its complexity.
Opt-in JIT compiler in CPython 3.15 that some people credit with real speedups, mostly on toy benchmarks. Critics say the gains are too small to justify its complexity.
29 people gave an opinion
- recommend it
- 13
- criticize it
- 16
- approval share
- 45%
Recommended in 3 of 13 months
- November 2025: not recommended
- December 2025: not recommended
- January 2026: not recommended
- February 2026: not recommended
- March 2026: recommended
- April 2026: not recommended
- May 2026: not recommended
- June 2026: 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
- 13 people recommend itNeeds 10 or more, met.
- 0.8 recommenders for every criticNeeds 2 to 1 or better, not met.
- Recommended in 3 of 13 monthsNeeds 4 or more, not 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
Real speedups in Python 3.15
“Good news. Python 3.15 adapts Pypy tracing approach to JIT and there are real performance gains now”
Comment from 14 Mar 2026 in “Python: The Optimization Ladder” “The experimental JIT was reported to finally breaking even and surpassing the default interpreter”
Comment from 6 Jun 2026 in “Python JIT project was asked to pause development” “the JIT is around 100% faster for toy programs like Richards”
Comment from 14 Mar 2026 in “Python: The Optimization Ladder” Technically exciting, worth keeping on main
“They belong on main because new optimizations and heuristics will always be generated.”
Comment from 27 Oct 2026 in “Python's experimental JIT to be removed” “It's unfortunate that a technically exciting new feature is being killed”
Comment from 27 Oct 2026 in “Python's experimental JIT to be removed” “Why not keep the JIT and let it evolve alongside the new framework?”
Comment from 5 Jun 2026 in “Python JIT project was asked to pause development”
What people warn about
Each mark is one comment
Project pulled or stalled upstream
“Kind of a shit move to suddenly pull the rug once they've finally gotten it working.”
Comment from 6 Jun 2026 in “Python JIT project was asked to pause development” “Seeing all of that get bogged down in committee bureaucracy now is just frustrating.”
Comment from 27 Oct 2026 in “Python's experimental JIT to be removed” “Now the new JIT is dying because of what seems to be a lack of upstream interest.”
Comment from 27 Oct 2026 in “Python's experimental JIT to be removed” - Comment from 27 Oct 2026 in “Python's experimental JIT to be removed”
- Comment from 27 Oct 2026 in “Python's experimental JIT to be removed”
Gains too small for complexity
“it's still only 15% faster than a simpler alternative. In a language that is 50x slower than the alternatives. Clearly not worth it.”
Comment from 6 Jun 2026 in “Python JIT project was asked to pause development” “Complicating the code base for occasional 50% speedups just isn't worth it.”
Comment from 6 Jun 2026 in “Python JIT project was asked to pause development” “best case 15% faster clearly isn't worth the complexity of a JIT”
Comment from 6 Jun 2026 in “Python JIT project was asked to pause development” - Comment from 27 Oct 2026 in “Python's experimental JIT to be removed”
Little measurable speedup overall
“the CPython JIT finally managed in 3.15 to be ~5% faster than the stock interpreter on x86_64”
Comment from 21 Apr 2026 in “How to Make a Fast Dynamic Language Interpreter” “The CPython JIT has barely had any impact on its performance.”
Comment from 8 May 2026 in “Mojo 1.0 Beta” “the performance of the JIT was always fairly underwhelming”
Comment from 27 Oct 2026 in “Python's experimental JIT to be removed” - Comment from 6 Jun 2026 in “Python JIT project was asked to pause development”
Better served by PyPy or YJIT
“While this is great, I expected faster CPython to eventually culminate into what YJIT for Ruby is.”
Comment from 14 Mar 2026 in “Python: The Optimization Ladder” “Perhaps if the money which was spent on the built-in JIT had been spent on PyPy we'd be somewhere.”
Comment from 28 Oct 2026 in “Python's experimental JIT to be removed”
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 JITThis page | 13 | 16 | 45% | 3 | — | — |
| YJIT | 10 | 2 | 83% | 6 | — | Approved |
| HotSpot JVM | 8 | 0 | 100% | 4 | — | — |
| ZJIT | 7 | 2 | 78% | 5 | — | — |
What people said
All 32 comments that mention it, newest first. Each links to the original comment.
“For the speed improvements, which we also need for a migration from on-prem to cloud, it's a no brainer”
“the implementation solid and stable”
“Perhaps if the money which was spent on the built-in JIT had been spent on PyPy we'd be somewhere.”
“I think its a meme but an interesting proof of concept nevertheless”
“Sad news, I put a lot of hope in this project.”
“From the state of the draft PEP it seems it doesn't and it won't ever.”
“the experiment was an ultimate failure (unlike free threading)”
“They belong on main because new optimizations and heuristics will always be generated.”
“the performance of the JIT was always fairly underwhelming”
“The alternative would be to have the bravery to say: this is the way forward to keep this language relevant into the future”
“Now the new JIT is dying because of what seems to be a lack of upstream interest.”
“the macrobenchmark benefits weren't _that_ exciting for a JIT”
“If you look at the reasons for this it seems like a good decision”
“It's unfortunate that a technically exciting new feature is being killed”
“Seeing all of that get bogged down in committee bureaucracy now is just frustrating.”
“it's still only 15% faster than a simpler alternative. In a language that is 50x slower than the alternatives. Clearly not worth it.”
“best case 15% faster clearly isn't worth the complexity of a JIT”
“the JIT implementation has not really been successful anyway”
“Complicating the code base for occasional 50% speedups just isn't worth it.”
“Kind of a shit move to suddenly pull the rug once they've finally gotten it working.”
“The experimental JIT was reported to finally breaking even and surpassing the default interpreter”
“Why not keep the JIT and let it evolve alongside the new framework?”
“still on baby steps and has to be explicitly enabled when installing the right build”
“The CPython JIT has barely had any impact on its performance.”
“the CPython JIT finally managed in 3.15 to be ~5% faster than the stock interpreter on x86_64”
“Opt-in starting from 3.15, or am I mistaken?”
“Great to see this going, Python also deserves a JIT,”
“the JIT is around 100% faster for toy programs like Richards”
“While this is great, I expected faster CPython to eventually culminate into what YJIT for Ruby is.”
“Good news. Python 3.15 adapts Pypy tracing approach to JIT and there are real performance gains now”
“something that CPython's JIT can't do”
“Any way you slice it, this is unimpressive.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.