Online Regex Tester & Debugger

• Real-time match highlighting as you type the pattern
• Supports JavaScript regex flags: global (g), case-insensitive (i), multiline (m)
• Shows numbered capture groups and named groups
• Test replacement patterns with $1, $2 backreferences
• Common patterns: email, URL, phone, IP address, date formats

Use Cases

Frequently Asked Questions

What regex syntax does this tester support?

It uses JavaScript's native RegExp engine, supporting all standard regex syntax including character classes, quantifiers, lookaheads, lookbehinds (ES2018+), named capture groups, and Unicode property escapes.

What regex flags are available?

All JavaScript regex flags: g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line boundaries), s (dotAll — . matches newlines), u (unicode), and y (sticky).

How do I test capture groups?

Add parentheses in your pattern to create capture groups. The tool displays all captured values with their group numbers. For named groups, use (?<name>pattern) syntax and the tool shows the group names.

Can I test regex replacement patterns?

Yes. Enter a replacement string using $1, $2 backreferences for captured groups, or $& for the full match. The tool shows the replacement result in real time.

Will my regex work the same in Python or Java?

Regex syntax varies between languages. This tester uses JavaScript regex. Most basic patterns work cross-language, but features like lookbehinds, named groups, and flags may differ in Python, Java, or Go.

Is this regex tester free?

Yes. Completely free, runs locally in your browser, and has no limits on pattern testing or registration requirements.