Kastavo

Regex Tester

Type the regular expression, the flags, and the test text — results appear automatically.

//

Processed locally in your browser.

How it works

Useful for developers validating patterns for validation, data extraction, or text replacement before using them in code. The search always finds every match in the text (not just the first), regardless of whether you include the "g" flag or not. Capture groups — the parenthesized parts of your pattern — appear listed under each match. If the regular expression has a syntax error, the tool shows the error message from your browser's own regex engine, without crashing the page.

Frequently asked questions

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