Regex Cheat Sheet
Quick reference for regular expression patterns. Searchable with examples. Click any pattern to copy.
Character Classes
Any character except newline
a.c → abc, a1c, a-c
Digit (0-9)
\d+ → 123, 42
Non-digit
\D+ → abc, !@#
Word character (a-z, A-Z, 0-9, _)
\w+ → hello_world
Non-word character
\W+ → @#$, !!
Whitespace (space, tab, newline)
a\sb → a b, a\tb
Non-whitespace
\S+ → hello
Any character in the set
[aeiou] → vowels
Any character NOT in the set
[^0-9] → non-digits
Character range (lowercase)
[a-z]+ → hello
Any letter
[A-Za-z]+ → Hello
Quantifiers
0 or more
ab*c → ac, abc, abbc
1 or more
ab+c → abc, abbc (not ac)
0 or 1 (optional)
colou?r → color, colour
Exactly n times
\d{3} → 123, 456
n or more times
\d{2,} → 12, 123, 1234
Between n and m times
\d{2,4} → 12, 123, 1234
0 or more (lazy/non-greedy)
<.*?> → shortest match
1 or more (lazy/non-greedy)
.+? → single char at a time
Anchors & Boundaries
Start of string/line
^Hello → starts with Hello
End of string/line
world$ → ends with world
Word boundary
\bcat\b → cat (not catch)
Non-word boundary
\Bcat → concatenate
Exact match (anchored)
^\d+$ → only digits
Groups & Alternation
Capturing group
(\d+) → captures digits
Non-capturing group
(?:ab)+ → ab, abab
Alternation (OR)
cat|dog → cat or dog
Backreference to group 1
(\w+)\s\1 → word word
Positive lookahead
\d(?=px) → digit before px
Negative lookahead
\d(?!px) → digit NOT before px
Positive lookbehind
(?<=\$)\d+ → digits after $
Negative lookbehind
(?<!\$)\d+ → digits NOT after $
Named capturing group
(?<year>\d{4}) → named year
Flags
Global - find all matches
/abc/g → all occurrences
Case-insensitive
/abc/i → ABC, abc, Abc
Multiline - ^ and $ match line starts/ends
/^hello/m → per line
Dotall - . matches newlines too
/a.b/s → a\nb
Unicode support
/\p{L}/u → any letter
Common Patterns
Email (basic)
user@example.com
URL (basic)
https://example.com/path
IPv4 address
192.168.1.1
Hex color
#ff5733, #ABC
Date (YYYY-MM-DD)
2024-01-15
Phone (E.164)
+14155551234
Strong password
Min 8, upper+lower+digit