Which regex flavour is used?

JavaScript (ECMAScript) regular expressions, as implemented in the browser's native RegExp engine. Syntax follows the ECMAScript 2023 standard.

What does the global flag (g) do?

With the global flag, all non-overlapping matches are found and listed. Without it, only the first match is returned.

What happens with an invalid regex?

An error badge appears below the pattern input showing the parse error. No crash, just a clear error message.

Regex match tester

Enter a regular expression pattern and a test string to see all matches highlighted in real time. Supports the global, case-insensitive, multiline, and dotAll flags.

Test string

0 matches

Enter a pattern and test string above

MODE

Runs entirely in your browser

How it works

The tool uses the browser's native JavaScript RegExp engine. Patterns are compiled with new RegExp(pattern, flags) and results are computed synchronously. Invalid patterns show an error badge, they never crash the page.

Processing runs in your browser

Both the pattern and the test string are processed entirely in your browser. Our servers are not involved at any point.

Related operations

For plain substring swaps without regex, try find and replace. To validate JSON patterns you are matching, use the JSON formatter. For decoding escape sequences in HTML attribute values, see HTML entities.

Frequently asked questions

Which regex flavour is used?: JavaScript (ECMAScript) regular expressions, as implemented in the browser's native RegExp engine. Syntax follows the ECMAScript 2023 standard.
What does the global flag (g) do?: With the global flag, all non-overlapping matches are found and listed. Without it, only the first match is returned.
What happens with an invalid regex?: An error badge appears below the pattern input showing the parse error. No crash, just a clear error message.

Regex match tester

How it works

Processing runs in your browser

Related operations

Frequently asked questions

Related tools