Regex Tester Online — Test Regular Expressions in Real Time

What is Regex Tester?

Metoolzy Regex Tester is a tool to test regular expressions directly in the browser. You enter a pattern and a test string → the matches are highlighted in real time.

Regex is an important skill for any developer — from validating emails, searching through logs, to parsing complex data.

Features

• Live matching — Results are highlighted as you type, no button click needed
• Capture groups — Clearly shows each capture group for every match
• Flag toggles — Enable/disable g (global), i (case-insensitive), m (multiline), s (dotAll)
• Match count — Counts total matches and their positions (index)
• Color coded — Each match is highlighted in a different color for easy distinction
• Client-side — Patterns and test strings are not sent anywhere

How to use

1. Visit Regex Tester
2. Enter the pattern in the /pattern/ box (example: \d+)
3. Select the flags to use (g, i, m, s)
4. Enter the test string into the textarea below
5. View results: matches are highlighted + a detailed list below

Common regex examples

Pattern	Purpose	Match example
\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b	Validate email	user@example.com
^(https?:\/\/)?(www\.)?[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}	Match URL	https://metoolzy.com
\b\d{3}[-.]?\d{3}[-.]?\d{4}\b	US phone number	123-456-7890
(\d{4})-(\d{2})-(\d{2})	Date YYYY-MM-DD	2025-01-15
(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d\d?)	IPv4 address	192.168.1.1

Frequently Asked Questions

What engine does Regex Tester use?

The JavaScript RegExp engine — the same engine used by Node.js and browsers.

Does it support lookbehinds?

Yes. JavaScript ES2018+ supports lookbehinds (?<=...) and (?<!...).

Are my patterns saved?

No. All processing is client-side, no data is sent to a server.

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