Regular Expressions Cheat Sheet
# Regular Expressions Cheat Sheet
## Anchors
- `^` — Start of string
- `$` — End of string
- `\b` — Word boundary
## Character Classes
- `.` — Any character
- `\d` — Digit [0-9]
- \w — Word char [a-zA-Z0-9_]
- \s — Whitespace
- [abc] — a, b, or c
- [^abc] — Not a, b, or c
- [a-z] — Range
## Quantifiers
- * — Zero or more
- + — One or more
- ? — Zero or one
- {n} — Exactly n
- {n,} — n or more
- {n,m} — Between n and m
## Groups & Alternation
- (abc) — Capture group
- (?:abc) — Non-capturing
- a|b — Alternation
## Lookahead/Lookbehind
- (?=...) — Positive lookahead
- (?!...) — Negative lookahead
- (?<=...) — Positive lookbehind
- (?<!...) — Negative lookbehind
## Common Patterns
- Email: ^[\w.-]+@[\w.-]+\.\w+$
- URL: ^https?://.+$
- IP: ^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$