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ToolNest AI
Free

Regex Tester

Test and debug regular expressions with live match highlighting.

Flags
Regular Expression
//g
Test String
0 chars

About Regex Tester

Write a regular expression and test it against a string in real time. Highlights all matches, lists capture groups, shows match count, and provides clear error messages for invalid patterns. Supports g, i, m, and s flags.

Frequently Asked Questions

This tool uses JavaScript's built-in RegExp engine, which follows the ECMAScript standard. It supports most common regex features including lookaheads, backreferences, and named groups.

g = global (find all matches), i = case-insensitive, m = multiline (^ and $ match line boundaries), s = dotAll (. matches newlines).

Yes. The tool lists all capture groups for each match, showing both numbered and named groups.

There is no hard limit, but very long strings or complex patterns with catastrophic backtracking may cause the browser to slow down temporarily.

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