Regex Tester
Test a regular expression against sample text, with matches highlighted live as you type. See every match and its capture groups.
Flags reference
g global (find all matches, always applied here internally), i case-insensitive, m multiline (^ and $ match line boundaries), s dotAll (. matches newlines), u unicode, y sticky.
Common questions
Does this use JavaScript regex syntax?
Yes, since it runs in your browser using JavaScript's native RegExp engine. That's the same syntax used in Node.js and most browser-side code, close to but not identical to PCRE (used by PHP, Python's re module differs slightly too).
Why does it always seem to act like the global flag is on?
So every match gets found and highlighted rather than stopping at the first one. Whatever you type in the flags field is still respected for everything else (case sensitivity, multiline, etc.), the global behavior is just always applied for finding all matches to display.
Is my test string sent anywhere?
No, matching happens entirely in your browser's JavaScript engine. Nothing is uploaded.