| . | any character except newline | |
| \w \d \s | word, digit, whitespace | |
| \W \D \S | not word, digit, whitespace | |
| [abc] | any of a, b, or c | |
| [^abc] | not a, b, or c | |
| [a-g] | character between a & g |
Anchors
| ^abc$ | start / end of the string | |
| \b \B | word, not-word boundary |
Escaped characters
| \. \* \\ | escaped special characters | |
| \t \n \r | tab, linefeed, carriage return |
Groups & Lookaround
| (abc) | capture group | |
| \1 | backreference to group #1 | |
| (?:abc) | non-capturing group | |
| (?=abc) | positive lookahead | |
| (?!abc) | negative lookahead |
Quantifiers & Alternation
| a* a+ a? | 0 or more, 1 or more, 0 or 1 | |
| a{5} a{2,} | exactly five, two or more | |
| a{1,3} | between one & three | |
| a+? a{2,}? | match as few as possible | |
| ab|cd | match ab or cd |
Ref: regexr.com
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