RE# regex engine
Shares rank 3 of 4 regex libraries by recommenders
People recommend RE# for fast matching with intersection, complement and unbounded lookarounds, and call its extended operators a real improvement over existing engines.
People recommend RE# for fast matching with intersection, complement and unbounded lookarounds, and call its extended operators a real improvement over existing engines.
6 people gave an opinion
- recommend it
- 5
- criticize it
- 1
- approval share
- 83%
Recommended in 1 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: not recommended
- July 2026: not recommended
- August 2026: not recommended
- September 2026: not recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it doesn’t carry the badge
- 5 people recommend itNeeds 10 or more, not met.
- 5 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 1 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
Intersection and complement operators
“even just the extended operators alone are a nice improvement over existing regex engines”
Comment from 4 Mar 2026 in “RE#: how we built the fastest regex engine in F#” “it's very much faster and much easier to use (with intersection and complement)”
Comment from 4 Mar 2026 in “RE#: how we built the fastest regex engine in F#” Fast on lookarounds and large patterns
“Unbounded lookarounds without performance penalty at search time are an exciting feature too.”
Comment from 4 Mar 2026 in “RE#: how we built the fastest regex engine in F#” “it's the fastest for large patterns and lookarounds”
Comment from 4 Mar 2026 in “RE#: how we built the fastest regex engine in F#”
Other regex libraries people recommend
The three most recommended other regex libraries, 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 |
|---|---|---|---|---|---|---|
| regex crate for Rust | 9 | 3 | 75% | 5 | — | — |
| PCRE | 6 | 4 | 60% | 5 | — | — |
| RE# regex engineThis page | 5 | 1 | 83% | 1 | — | — |
| regex-utils | 5 | 0 | 100% | 3 | — | — |
What people said
All 9 comments that mention it, newest first. Each links to the original comment.
“There's a lot of nice things you get for free with the two pass approach”
“I think that should be a reasonable approach, but the library is still new”
“No submatches, lazy compilation”
“it's very much faster and much easier to use (with intersection and complement)”
“the paper is high quality”
“it's the fastest for large patterns and lookarounds”
“But if you want all matches it is very good.”
“even just the extended operators alone are a nice improvement over existing regex engines”
“Unbounded lookarounds without performance penalty at search time are an exciting feature too.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.