What is a Regular Expression?

A Regular Expression (Regex) is a sequence of characters that specifies a search pattern. They are used for finding, replacing, and validating strings.

Which Regex flavor is supported?

This tool uses the JavaScript (ECMAScript) regex engine, which is standard for web development and Node.js applications.

What do the flags do?

Flags modify the search behavior. "g" finds all matches (global), "i" ignores case, and "m" allows anchors like ^ and $ to match start/end of lines.

How do I match a digit?

Use the character class "\d" to match any digit from 0 to 9.

Regex Tester

Regex Tester Overview

Test and debug regular expressions

Our Regex Tester is a powerful online utility for building, testing, and debugging JavaScript regular expressions. It provides real-time matching, syntax highlighting, and capture group analysis to help you master regex patterns. Whether you are validating emails, parsing logs, or extracting data, this tool offers immediate feedback on your patterns against test strings.

How to Use Regex Tester

Enter your regex pattern (e.g., ^[a-z]+$) in the input field.
Add flags like "g" (global) or "i" (case-insensitive) as needed.
Type or paste your test string in the text area.
Instantly view highlighted matches and extracted capture groups.

Frequently Asked Questions

What is a Regular Expression?: A Regular Expression (Regex) is a sequence of characters that specifies a search pattern. They are used for finding, replacing, and validating strings.
Which Regex flavor is supported?: This tool uses the JavaScript (ECMAScript) regex engine, which is standard for web development and Node.js applications.
What do the flags do?: Flags modify the search behavior. "g" finds all matches (global), "i" ignores case, and "m" allows anchors like ^ and $ to match start/end of lines.
How do I match a digit?: Use the character class "\d" to match any digit from 0 to 9.

Related Dev Tools

IP Geolocation - Find location data for any IP address
Domain Availability - Check if a domain name is available for registration
React Component Gen - Generate boilerplate for React components
.htaccess File Generator - Create Apache redirects and security rules
robots.txt Tester - Test if a specific URL is allowed by robots.txt
JSON to TOON Converter - Optimize JSON for LLMs (30-60% Token Reduction)
UUID Generator - Generate unique identifiers (UUIDs/GUIDs) instantly
Hash Generator - Generate cryptographic hashes securely