Test regular expressions with live match highlighting.
.Any char (except newline)\dDigit [0-9]\wWord char [A-Za-z0-9_]\sWhitespace\bWord boundary^Start of string / line$End of string / line*0 or more+1 or more?0 or 1 (optional){n,m}Between n and m times(abc)Capture group(?:abc)Non-capturing group(?<n>abc)Named groupa|ba or b[abc]Character class[^abc]Negated class\p{L}Unicode letter (u flag)