Regex Cheatsheet for Developers

Essentials

• ^ / $ — start / end of string (or line with m)
• . — any character except newline (unless s)
• *, +, ?, {n,m} — quantifiers
• (…) — capturing group; (?:…) — non-capturing
• Flags: g i m s u y

Watch out for

Nested .* with alternation can cause catastrophic backtracking. Prefer tighter character classes and test edge cases in Regex Lab.