Regex Tester

Test regular expressions against text in real time. Matches are highlighted as you type. Uses the JavaScript ECMAScript regex engine — free, instant, no install.

What is a Regex Tester?

A regex tester (regular expression tester) lets you write and test regular expressions against sample text in real time, highlighting matches as you type. This tool uses JavaScript’s built-in RegExp engine, which follows the ECMAScript standard and is identical to what runs in your browser and Node.js.

Regex Flags Explained

• g (global) — find all matches, not just the first one
• i (ignore case) — match uppercase and lowercase interchangeably
• m (multiline) — ^ and $ match start/end of each line
• s (dotAll) — . matches newline characters as well

Common Regex Patterns

• Email: [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}
• URL: https?://[^\s]+
• Phone (US): \(?\d{3}\)?[-.\s]?\d{3}[-.\s]?\d{4}
• IPv4: \b(?:\d{1,3}\.){3}\d{1,3}\b
• Hex color: #([0-9a-fA-F]{3}|[0-9a-fA-F]{6})\b

Frequently Asked Questions

Which regex engine does this tool use?

This tool uses the JavaScript ECMAScript regex engine — the same engine used in Chrome, Firefox, Safari, and Node.js. It supports most common regex syntax but does not support lookbehind in older browsers or PCRE-specific syntax like \K.

How do I match newlines?

Enable the s (dotAll) flag to make . match newline characters, or use [\s\S] as a workaround without the flag.