Regex Tester - Real-Time Match Highlighting

How to Use

1. Enter your regular expression pattern in the top input field (no slashes needed)
2. Set flags (g, i, m, s, u) using the checkboxes. The g flag (global match) is ON by default
3. Enter the text you want to match against in the test string area
4. Matched portions are highlighted in real time, along with the match count and capture groups

Usage Examples

Matching email addresses:
Pattern: [\w.+-]+@[\w-]+\.[\w.]+
Test: user@example.com, invalid-email
→ Matches: user@example.com

Matching digits only:
Pattern: \d+
Test: abc 123 def 456
→ Matches: 123, 456

Using capture groups:
Pattern: (\d{4})-(\d{2})-(\d{2})
Test: 2026-02-19
→ Group 1: 2026, Group 2: 02, Group 3: 19

FAQ

Is my data sent to a server?

No. All processing is done by your browser's JavaScript engine.

What regex flavor is used?

JavaScript's native RegExp is used. It may differ slightly from PCRE (Perl-compatible regex).

What happens if I turn off the g flag?

Only the first match is returned (equivalent to match() without global). It's generally recommended to keep g enabled to see all matches.

Could a complex pattern freeze the browser?

Processing is capped at 10,000 matches. Be cautious with ReDoS-prone patterns (catastrophic backtracking).

Are named capture groups (?<name>...) supported?

All syntax supported by JavaScript is available, including named capture groups. However, the results table shows them by group number.

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