Question 1

What regex flavor does this tester use?

Accepted Answer

This tool uses JavaScript (ECMAScript) regular expressions, which is the native regex engine built into all browsers. It supports standard syntax including character classes, quantifiers, groups, lookaheads and named capture groups.

Question 2

What do the regex flags mean?

Accepted Answer

g = global (find all matches), i = case-insensitive, m = multiline (^ and $ match line boundaries), s = dotAll (. matches newlines), u = unicode mode, y = sticky (match from lastIndex). Click the flag buttons to toggle them.

Question 3

Is my regex data sent to a server?

Accepted Answer

No. All regex testing happens entirely in your browser. Your patterns and test text never leave your device.

Question 4

How do I use capture groups?

Accepted Answer

Use parentheses to create capture groups: (\d+) captures digits, (?<year>\d{4}) creates a named group. The results table shows each match with its group values for easy debugging.

`.`		`\\d`
`\\w`		`\\s`
`[abc]`		`[^abc]`
`*`		`+`
`?`		`{n,m}`
`^`		`$`

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