Regex Cheatsheet: Complete Guide to Regular Expressions
2026-03-28 8 min read
Master regular expressions with this practical reference. Covers anchors, character classes, quantifiers, groups, lookaheads, and real-world pattern examples.
Regular expressions (regex) are one of the most powerful and most feared tools in a developer's toolkit. Once you understand the patterns, you can parse, validate, and transform text with a single line of code. This cheatsheet covers everything you need.
Anchors
^— Start of string (or line in multiline mode)$— End of string (or line in multiline mode)\b— Word boundary\B— Non-word boundary
Character Classes
.— Any character except newline\d— Digit [0-9]\D— Non-digit\w— Word character [a-zA-Z0-9_]\s— Whitespace (space, tab, newline)[abc]— a, b, or c[^abc]— Not a, b, or c[a-z]— Lowercase letter
Quantifiers
*— 0 or more+— 1 or more?— 0 or 1 (also makes quantifiers lazy){n}— Exactly n times{n,m}— Between n and m times
Groups and Lookaheads
(abc)— Capturing group(?:abc)— Non-capturing group(?=abc)— Positive lookahead(?!abc)— Negative lookaheada|b— a or b
Real-World Examples
- Email:
^[\w.+-]+@[\w-]+\.[a-z]{2,}$ - URL:
^https?://[^\s]+$ - Indian phone:
^[6-9]\d{9}$ - Date (YYYY-MM-DD):
^\d{4}-\d{2}-\d{2}$