Regex Golf Arena

How it works

Regex golf with built-in puzzles: write one JavaScript regular expression that matches every string on the “match” list and none on the “don’t match” list. Shorter is better; perfect solutions can join a per-puzzle top-20 leaderboard. Use “dry run” to test without submitting.

• Your pattern is compiled with JavaScript’s RegExp (flags i/u optional) and tested against every string with RegExp.test, so it may match anywhere in the string unless you anchor it.
• Score = 10 × (strings on the match list that match + strings on the don’t-match list that do not match) − regex length, as in classic regex golf. A solution is perfect when every string is classified correctly.
• Safety: patterns are limited to 200 characters, control characters are refused, and patterns where an unbounded quantifier repeats a group that contains another variable quantifier or an alternation — the classic catastrophic-backtracking shapes such as (a+)+ or (a|aa)* — are rejected before running. The puzzle strings are short (at most 12 characters), which bounds the remaining work.
• Leaderboard: only perfect, non-dry-run solutions are entered, ranked by length, then date. Each puzzle keeps the top 20; an identical regex only counts once, and each nickname keeps its best entry. Only nickname, length, score and date are shown — never the regex — so nobody gets spoilers.