Question 1

Which regex flavor does this use?

Accepted Answer

JavaScript's native RegExp engine (ECMAScript regex), running in your own browser — the same engine your browser's console or a Node.js script would use.

Question 2

What do the flags (g, i, m, s, u, y) mean?

Accepted Answer

g = global (find all matches, not just the first), i = case-insensitive, m = multiline (^ and $ match line boundaries), s = dotAll (. matches newlines), u = full Unicode mode, y = sticky (match only at lastIndex).

Question 3

Why aren't capture groups showing up?

Accepted Answer

Capture groups only appear in the match list, not the inline highlight. Make sure your pattern actually contains parentheses — non-capturing groups (?:...) intentionally don't produce a group entry.

Question 4

Is my test string sent anywhere?

Accepted Answer

No — matching runs entirely client-side against JavaScript's built-in regex engine. Nothing you type into the pattern or test string fields leaves your browser.

Regex Tester

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