Javascript Regex Tester
Test a regular expression against a string with live match highlighting.
Highlights every match live as you type, using JavaScript's own RegExp engine (the exact engine your code will run with). Runs entirely in your browser; nothing you type is sent anywhere.
What is Javascript Regex Tester?
Type a pattern and a test string and see every match highlighted instantly, using JavaScript's own RegExp engine — the exact engine your code will actually run with, not an approximation. That distinction matters more than it sounds: regex flavors differ subtly between languages, and a pattern that behaves one way in, say, Python's `re` module can behave differently in JavaScript. Testing against the real `RegExp` object here means what you see is exactly what `String.prototype.match` or `.replace` would do in your actual code, computed live in your browser as you type.
FAQ
All of JavaScript's regex flags — g, i, m, s, u, y — type them directly into the flags field.
A pattern that can match an empty string (like `a*`) could otherwise loop forever finding "matches" at the same position; this tool stops there rather than hang.