What dialect does this use?

JavaScript regex (ECMAScript). Lookbehinds, named groups, and Unicode property escapes are supported in modern browsers.

How do I reference capture groups in the replacement?

Use $1, $2, $& for the full match, or $ for named groups.

Is there a match limit?

The first 10,000 iterations are captured to keep the UI responsive; the first 50 are shown in the match list.

Is my data sent anywhere?

No. Patterns and test strings run only in your browser, and the auto-save keeps them in your local storage.

Regex Tester

Developer

Write a regular expression, toggle flags, and see matches highlighted in your test string instantly. Capture groups are listed per match, and you can preview a replacement on the side. Runs entirely in your browser using the native JavaScript RegExp engine.

—

Pattern

Flags

Test string

Matches2 match(es)

Contact me at jane@example.com or john@test.io for details.

#1 @14jane@example.com
#2 @34john@test.io

Replace with

Replacement preview

Contact me at [redacted] or [redacted] for details.

How to use

Enter a regex pattern (without delimiters).
Toggle flags: g (global), i (case-insensitive), m (multiline), s (dotall), u (unicode).
Type or paste a test string — matches highlight as you type.
Provide a replacement string to preview the result.

Frequently asked questions

What dialect does this use?: JavaScript regex (ECMAScript). Lookbehinds, named groups, and Unicode property escapes are supported in modern browsers.
How do I reference capture groups in the replacement?: Use $1, $2, $& for the full match, or $<name> for named groups.
Is there a match limit?: The first 10,000 iterations are captured to keep the UI responsive; the first 50 are shown in the match list.
Is my data sent anywhere?: No. Patterns and test strings run only in your browser, and the auto-save keeps them in your local storage.