Regex Tester
Test, debug, and validate regular expressions instantly. Supports flags, capture groups, match highlighting, and replace.
💡 Finding This Regex Tester Useful?
Get the complete standalone version — 100% offline, no dependencies, works anywhere. Perfect for developers who test regex patterns regularly.
🛒 Get the Standalone Version🔍 What Is a Regex Tester?
A Regex Tester (also called a regular expression tester or regex debugger) is an interactive tool that lets you test regular expressions against sample text in real time. It shows you which parts of your text match the pattern, highlights capture groups, and helps you debug complex regex patterns.
✨ Key Features
Match Testing
Test your regex against any text. See exactly which parts match, with clear highlighting of matches and groups.
Full Flag Support
Toggle g, i, m, s, and u flags to fine-tune your regex behavior.
Replace & Transform
Substitute matches with custom strings. Supports $1, $2, etc. for capture groups.
Highlight Mode
Visually see matches and groups directly in the output, perfect for understanding complex patterns.
Match Statistics
Instant feedback: total matches, capture group count, and match length.
Sample Data
Click Sample to load a demo pattern and see the tool in action.
📖 How to Use the Regex Tester
- Enter your regex pattern in the "Regular Expression" field. Toggle flags like g, i, m, s, u as needed.
- Paste or type your test text in the "Test String" textarea.
- Click Test to see all matches with capture groups and total count.
- Use Replace to substitute matches. Reference groups with $1, $2, etc.
- Toggle Highlight to visually see matches and groups in the output.
- Copy results or Clear to start fresh.
💡 Pro tip: Press Ctrl+Enter to run the test instantly.
🎯 Practical Use Cases
Data Validation
Test regex for validating emails, phone numbers, URLs, and structured data.
Log Analysis
Extract patterns from server logs and application output.
Text Processing
Find and replace text in documents and configuration files.
Code Search & Refactoring
Search patterns in source code and refactor variable names.
Data Extraction
Extract dates, IDs, or keywords using capture groups.
Learning Regex
Experiment with patterns to understand how they work.
❓ Frequently Asked Questions
A Regex Tester lets you test regular expressions against sample text in real time. Developers use it to validate data, extract information, search code, and learn regex syntax without writing test scripts.
100% safe. Everything runs in your browser using vanilla JavaScript. No data is ever sent to any server.
This tool uses the JavaScript RegExp engine, built into every modern browser. It supports capture groups, character classes, quantifiers, and flags like g, i, m, s, u.
Yes! Once the page loads, the tool works entirely offline.
Completely free, forever. No sign-up, no hidden fees.
👨💻 About the Author — GenieDevs
📦 Get the Standalone Version
🔍 Regex Tester – Standalone Edition
Get the complete, self-contained HTML version of this tool. Perfect for offline use, intranet deployments, or embedding in your own projects.