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Free online regex tester with real-time highlighting, pattern generator, and smart explanation. Test JavaScript regex patterns, debug expressions, and export code for multiple languages.
Test and debug regular expressions with real-time feedback and smart explanations
Type your regex pattern or use the generator to build one automatically.
Paste your test string to see real-time highlighting of all matches.
Read the explanation to understand what each part of your regex does.
Export your regex for JavaScript, Python, PHP, or share via URL.
See matches highlighted instantly as you type. No refresh needed.
Breaks down complex patterns into human-readable explanations.
Copy code snippets for JavaScript, Python, and PHP instantly.
Build regex patterns using simple input fields—no memorization needed.
Validate email addresses in web forms
Extract URLs from text or HTML content
Format and validate phone numbers
Match credit card patterns for payment validation
Parse log files and extract structured data
Search and replace text with pattern matching
Our regex tester combines real-time testing with smart explanations and ReDoS protection to help you build better patterns.
Your data never leaves your browser—complete privacy guaranteed
See matches highlighted instantly with visual feedback as you type
Prevents browser hangs from catastrophic backtracking patterns
Share compressed state links for easy collaboration
Full support for global, case-insensitive, and multiline flags
Shows exactly how many results were found in real-time
Use (?:...) instead of (...) when you don't need to extract the group—it's faster.
Avoid nested quantifiers like (a+)+ which can cause catastrophic backtracking.
Use \d instead of . when matching numbers—it's more precise and performant.
Click 'Share URL' to generate a compressed link you can send to teammates.
This tool uses JavaScript's built-in RegExp engine, which is compatible with ECMAScript regex syntax. Patterns work in browsers, Node.js, and most modern JavaScript environments.
The tool runs regex tests with a timeout mechanism. If execution takes too long (indicating catastrophic backtracking), it's automatically aborted to prevent browser hangs.
Yes! Click the 'Share URL' button to generate a compressed link containing your regex, test string, and flags. Anyone with the link can view and modify your test.
The global flag (g) makes the regex match all occurrences, not just the first. The multiline flag (m) makes ^ and $ match line boundaries, not just string boundaries.
No! All regex testing happens 100% in your browser using JavaScript. Your patterns and test strings never leave your device, ensuring complete privacy.
The explainer parses common regex syntax and provides descriptions for quantifiers, character classes, anchors, and groups. Complex lookarounds and advanced features are also explained in detail.