Regex Tester

Test and debug regular expressions in real-time with match highlighting, capture groups, replacement preview, and pattern explanation. Supports all JavaScript regex features.

What is Regex Tester?

A Regex Tester lets you build, test, and debug regular expressions interactively. It highlights matches in real-time, shows capture groups, and explains pattern components. Essential for developers working with text parsing, validation, and data extraction.

How to Use Regex Tester

Enter your regex pattern in the top field. Type or paste test text below. Matches are highlighted in real-time. Toggle flags (g, i, m, s, u, y) as needed. Use the Replace field to preview substitutions. Click Common Patterns for pre-built examples.

FAQ

What regex flavor does this use?

This tool uses JavaScript regular expressions (ECMAScript), which is the standard for web browsers and Node.js.

What do the flags do?

Common flags include 'g' for global (all matches), 'i' for case-insensitive, 'm' for multiline, 's' for dotAll (dot matches newlines), 'u' for Unicode, and 'y' for sticky.

Can I use lookahead and lookbehind?

Yes, JavaScript supports positive/negative lookahead (?=, ?!) and lookbehind (?<=, ?<!). These are zero-width assertions that match without consuming characters.