Regex Tester, Matcher & Debugger
Interactive Regular Expression tester supporting global, multiline, case-insensitive, and unicode flags. Features live match highlights, capture group breakdown, and regex cheat sheet.
Key Features & Security Guarantees
- ✓ Real-time colorized match highlighting across multi-line text
- ✓ Capture group decomposition (Group 1, 2, and named groups)
- ✓ Interactive flag toggles (Global, Case-insensitive, Multiline, DotAll, Unicode)
- ✓ Built-in template library for emails, URLs, dates, and phone numbers
How to Use This Utility
Enter Regular Expression: Type your regex pattern (e.g. ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,}$) and select flags.
Input Test String: Paste sample text to test matches, or select a pre-configured template.
Inspect Matches & Groups: View highlighted matches in the editor and explore capture groups in the breakdown panel.
Technical Architecture & How It Works
The Regex Tester utilizes the native JavaScript RegExp compilation engine to evaluate pattern expressions against sample strings in real time. It features a match index offset calculator that breaks down start/end positions, capture groups, and total execution performance.
Security Verification: Your test strings and regex patterns are evaluated entirely in local browser memory.
Underlying Browser APIs
Real-World Developer Use Cases
Form Input Validation
Test patterns for passwords, postal codes, and email inputs before adding them to frontend forms.
Log File Scraping & Extraction
Extract IP addresses, timestamps, and error codes from server log dumps.
Frequently Asked Questions
Which regular expression flags are supported?
We support all standard ECMAScript flags: g (global), i (case-insensitive), m (multiline), s (dotAll), and u (unicode).
Can I see named capture groups in the match breakdown?
Yes. Both indexed ($1, $2) and named capture groups (?<name>) are displayed in the results table.
Are there built-in regex templates for common patterns?
Yes! We provide 1-click templates for Email addresses, URLs, IPv4/IPv6 addresses, dates, and UUIDs.