| . | Any character (except newline) |
| \d | Digit [0-9] |
| \D | Not digit [^0-9] |
| \w | Word character [a-zA-Z0-9_] |
| \W | Non-word character |
| \s | Whitespace |
| \S | Non-whitespace |
| \n | Newline |
| \t | Tab |
| \xHH | Hex character |
| \uHHHH | Unicode character |
| * | Zero or more |
| + | One or more |
| ? | Zero or one (optional) |
| {n} | Exactly n times |
| {n,} | n or more times |
| {n,m} | Between n and m times |
| *? | Zero or more (lazy) |
| +? | One or more (lazy) |
| ?? | Zero or one (lazy) |
| ^ | Start of string/line |
| $ | End of string/line |
| \b | Word boundary |
| \B | Non-word boundary |
| \A | Start of string only |
| \Z | End of string only |
| (...) | Capturing group |
| (?:...) | Non-capturing group |
| (?<name>...) | Named capturing group |
| \1, \2 | Backreference |
| (?=...) | Lookahead |
| (?!...) | Negative lookahead |
| (?<=...) | Lookbehind |
| (?<!...) | Negative lookbehind |
| [abc] | Any of a, b, or c |
| [^abc] | Not a, b, or c |
| [a-z] | Character range a to z |
| [a-zA-Z] | Uppercase and lowercase |
| g | Global - find all matches |
| i | Case insensitive |
| m | Multiline (^/$ per line) |
| s | Dotall (. matches \n) |
| u | Unicode support |
| $& | Entire match |
| $1, $2 | Capture group |
| $` | Before match |
| $' | After match |
| $$ | Literal $ |
| | | Alternation (OR) |
| \ | Escape special character |
| \k<name> | Named backreference |