Question 1

What regex flavour does this tool use?

Accepted Answer

This tool uses JavaScript (ECMAScript) regular expressions, which are supported natively in all modern browsers. JavaScript regex supports most common features: character classes, quantifiers, groups, lookaheads, and lookbehinds.

Question 2

What do the flags mean?

Accepted Answer

g (global) finds all matches. i (case insensitive) ignores letter case. m (multiline) makes ^ and $ match start/end of each line. s (dotAll) makes . match newline characters. u (unicode) enables full Unicode support.

Question 3

How do I match a literal special character?

Accepted Answer

Escape it with a backslash. For example, to match a dot (.) literally, use \. To match a parenthesis, use $ or $.

Question 4

What are capture groups?

Accepted Answer

Capture groups are portions of a regex wrapped in parentheses that capture the matched text. For example, (\d{4}) captures a 4-digit year. Named groups use the syntax (?<name>pattern). This tool shows captured groups in the match details.

Question 5

Can I use this to test email or URL validation regex?

Accepted Answer

Yes. Paste your validation regex and test it against sample inputs to see which strings match and which do not. This is useful for validating email addresses, URLs, phone numbers, postal codes, and more.

Regex Tester

How to Use This Regex Tester

Common Regex Patterns

Frequently Asked Questions

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