Question 1

Which regex flavor does this use?

Accepted Answer

It uses the JavaScript (ECMAScript) regex engine built into your browser, so results match what you would get in JavaScript code.

Question 2

What do the flags g, i, m, s, u, d mean?

Accepted Answer

g = global (all matches), i = ignore case, m = multiline (^ and $ per line), s = dotall (. matches newlines), u = unicode, d = generate match indices.

Question 3

Are capture groups supported?

Accepted Answer

Yes. Both numbered groups and named groups (?<name>...) are shown, along with their matched text and positions.

Question 4

Is my test data private?

Accepted Answer

Yes. The pattern and text never leave your browser; matching runs entirely on your device.

Question 5

Why is my pattern marked invalid?

Accepted Answer

The pattern has a syntax error for the JavaScript engine — for example an unbalanced bracket or an invalid escape. Fix the highlighted issue and matching resumes.

Regex Tester