Write a pattern, test against text, see matches highlighted live
.Any character\dDigit (0-9)\wWord char (a-z, 0-9, _)\sWhitespace\bWord boundary^Start of string$End of string*0 or more+1 or more?0 or 1{n}Exactly n{n,m}Between n and m[abc]Character class[^abc]Not in class(abc)Capture groupa|bAlternation (or)(?:abc)Non-capture group(?=abc)Lookahead