Matches
0 found
Highlighted matches will appear here...
Anchors
| Anchor | Description | Example | Matches |
|---|---|---|---|
| ^ | Start of string or line | ^Team | "Team" at start |
| $ | End of string or line | end$ | "end" at end |
| \b | Word boundary | \bword\b | whole word only |
| \B | Not word boundary | \Bend | "end" inside word |
Character Classes
| Class | Description | Equivalent |
|---|---|---|
| \d | Digit | [0-9] |
| \D | Not a digit | [^0-9] |
| \w | Word character | [a-zA-Z0-9_] |
| \W | Not a word character | [^a-zA-Z0-9_] |
| \s | Whitespace | [ \t\n\r\f\v] |
| \S | Not whitespace | [^ \t\n\r\f\v] |
| . | Any character (except newline) | - |
| [abc] | Any of a, b, or c | - |
| [^abc] | Not a, b, or c | - |
| [a-z] | Range: a to z | - |
Quantifiers
| Quantifier | Description | Example |
|---|---|---|
| * | 0 or more | a* |
| + | 1 or more | a+ |
| ? | 0 or 1 | colou?r |
| {n} | Exactly n | \d{4} |
| {n,} | n or more | \d{2,} |
| {n,m} | Between n and m | \d{2,4} |
| *? | 0 or more (lazy) | a*? |
| +? | 1 or more (lazy) | a+? |
Groups & References
| Syntax | Description | Example |
|---|---|---|
| (...) | Capturing group | (abc) |
| (?:...) | Non-capturing group | (?:abc) |
| (?<name>...) | Named capturing group | (?<year>\d{4}) |
| \1, \2 | Backreference | (a)\1 |
| a|b | Alternation (or) | cat|dog |
Assertions (Lookahead/Lookbehind)
| Assertion | Description | Example |
|---|---|---|
| (?=...) | Positive lookahead | foo(?=bar) |
| (?!...) | Negative lookahead | foo(?!bar) |
| (?<=...) | Positive lookbehind | (?<=foo)bar |
| (?<!...) | Negative lookbehind | (?<!foo)bar |
Flags
| Flag | Description |
|---|---|
| g | Global - find all matches, not just the first |
| i | Case-insensitive matching |
| m | Multiline - ^ and $ match line boundaries |
| s | Dotall - . matches newlines too |
| u | Unicode - enables full Unicode support |
How it works
Enter a regular expression pattern and test string to see matches highlighted in real-time. Toggle regex flags to modify matching behavior.
Tips:
-
Use the
gflag to find all matches instead of just the first one - Click on a match in the results to see its position and capture groups
- The cheatsheet tab provides a quick reference for common regex syntax
- This tool uses JavaScript's RegExp engine, which supports most common regex features