The Essential Regex Syntax Reference
**Character Classes:** - `.` — Any character except newline - `\d` — Any digit [0-9] - `\w` — Word character [a-zA-Z0-9_] - `\s` — Whitespace (space, tab, newline) - `[abc]` — Any of a, b, or c - `[^abc]` — Any character except a, b, or c **Quantifiers:** - `*` — 0 or more - `+` — 1 or more - `?` — 0 or 1 (optional) - `{3}` — Exactly 3 times - `{3,6}` — Between 3 and 6 times **Anchors:** - `^` — Start of string (or line in multiline mode) - `$` — End of string (or line in multiline mode) - `\b` — Word boundary
10 Real-World Regex Patterns for Developers
**Email validation (basic):** `/^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/` **URL detection:** `/https?:\/\/(www\.)?[-a-zA-Z0-9@:%._+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}/` **IPv4 address:** `/^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/` **Date in YYYY-MM-DD format:** `/^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$/` **Password strength (min 8 chars, uppercase, lowercase, digit):** `/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$/` **Hex color code:** `/^#([a-fA-F0-9]{6}|[a-fA-F0-9]{3})$/` Test all of these instantly in our [Regex Tester](/regex-tester).
Conclusion
Regular expressions are a skill that pays compound dividends. Every pattern you learn eliminates dozens of lines of conditional logic. Practice with our interactive [Regex Tester](/regex-tester) — paste any pattern and test it against real input with live match highlighting. Bookmark this guide as a reference for your most-used patterns.