Regex Tester

Character classes

• .Any character except newline— a.c → abc, a2c
• \dA digit (0–9)— \d\d → 42
• \wWord character (a–z, 0–9, _)— \w+ → hello_1
• \sWhitespace (space, tab, newline)— a\sb → 'a b'
• [abc]Any one of a, b, or c— [aeiou] → a vowel
• [^abc]Any character except a, b, c— [^0-9] → non-digit
• [a-z]A range of characters— [A-Z] → any capital

Anchors & boundaries

• ^Start of the string / line— ^Hi → line starting 'Hi'
• $End of the string / line— end$ → line ending 'end'
• \bA word boundary— \bcat\b → the word 'cat'

Quantifiers

• *Zero or more— ab* → a, ab, abbb
• +One or more— ab+ → ab, abbb
• ?Optional (zero or one)— colou?r → color, colour
• {3}Exactly 3 times— \d{3} → 123
• {2,4}Between 2 and 4 times— \d{2,4} → 12–1234
• *?Lazy — as few as possible— <.*?> → shortest tag

Groups & alternation

• (abc)Capturing group— (ab)+ → abab
• (?:abc)Non-capturing group— (?:ab)+ → groups without capturing
• (?<name>…)Named capturing group— (?<year>\d{4})
• a|bMatch a OR b— cat|dog → cat, dog
• (?=…)Lookahead (followed by)— \d(?=px) → digit before 'px'

Flags

• gGlobal — find all matches— /a/g
• iCase-insensitive— /abc/i → ABC
• mMultiline — ^ and $ per line— /^x/m
• sDotall — . matches newline too— /a.b/s