Regex Tester
Build and test regular expressions with real-time match highlighting.
Codestable
//g
TEXT
0 matches
No matches found.
hello world\n1234
About Regex Tester
The Regex Tester is an interactive, visual environment for building and debugging Regular Expressions. It features real-time highlighting, group extraction, and detailed explanations of your pattern syntax.
How to Use
1
Type your Regular Expression pattern into the top input (e.g., `^[a-z]+$`).
2
Toggle specific flags like `g` (global), `i` (case-insensitive), or `m` (multiline).
3
Paste your test text into the editor below.
4
Matches and capturing groups will be instantly highlighted.
Real-World Examples
Extracting Email Addresses
Use a regex pattern to safely extract all email addresses from a large block of unstructured text.
Input
Pattern: \b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b
Flags: gi
Text: Contact us at support@example.comOutput
Match 1: support@example.com
Best Practices
- Always test your regex against edge cases, such as empty strings, extremely long inputs, or unexpected characters, to prevent ReDoS (Regular Expression Denial of Service) vulnerabilities.
Pro Tips
Use capturing groups `(...)` to isolate specific parts of a match, which will be extracted into a separate list for easy viewing.
Frequently Asked Questions
Which regex flavor is supported?
The tool utilizes the modern JavaScript (ECMAScript) RegExp engine.
Is my data secure?
Absolutely. All processing is done locally in your browser.
Security & Privacy
Your regex evaluations run safely within your browser's JavaScript engine. No test data or patterns are logged remotely.