What is RegEx Lab?
Regular expressions (regex) are powerful patterns used for matching, searching, and manipulating text. They are essential for tasks like input validation, data extraction, search-and-replace operations, and log parsing. However, regex syntax can be notoriously difficult to read and write, with cryptic symbols like (?<=), \b, and [^]. RegEx Lab provides an interactive environment to build, test, and understand regular expressions with real-time matching, visual highlighting, and AI-powered explanations that describe what each part of your pattern does in plain English.
Why Use This Tool?
Writing regex without proper tooling is frustrating and error-prone. Common challenges include: understanding what complex patterns actually match, debugging why a pattern doesn't capture what you expect, and learning the differences between regex flavors (JavaScript, Python, PCRE). RegEx Lab solves these problems with instant visual feedback - matches are highlighted as you type, capturing groups are color-coded, and our AI can explain any pattern in plain language. For example, paste "(?<=[\s])#\w+" and get: "Matches hashtags preceded by whitespace, capturing the # and word characters."
How to Use RegEx Lab
- Enter your regex pattern in the pattern field
- Paste or type your test string in the text area
- Matches are instantly highlighted with different colors for capturing groups
- Toggle flags (g, i, m, s, u) using the buttons above the pattern
- Click "Explain with AI" to get a plain English breakdown of the pattern
- View match details including groups, indices, and named captures
- Export matches as an array or use the replace function to transform text
Features
- Real-time matching with instant visual highlighting
- Color-coded capturing groups and named captures
- AI-powered pattern explanation in plain English
- Support for all JavaScript regex flags (g, i, m, s, u, y)
- Match statistics: count, positions, execution time
- Replace mode with backreference support ($1, $2, etc.)
- Common pattern library with 50+ pre-built patterns
- Regex cheat sheet with syntax reference
- Export matches as JSON array or copy individually
Common Use Cases
- Form Validation: Test email, phone, and URL validation patterns
- Data Extraction: Extract specific data from logs, HTML, or CSV
- Search and Replace: Transform text using capture group references
- Log Analysis: Parse timestamps, IP addresses, and error codes
- Code Refactoring: Find and replace patterns across codebases
Tips & Best Practices
- ✓ Start simple and build up complexity incrementally
- ✓ Use non-capturing groups (?:) when you don't need the match
- ✓ Test edge cases: empty strings, special characters, unicode
- ✓ Use the AI explainer to understand complex patterns before modifying them
How It Compares to Alternatives
Regex101.com is excellent for detailed debugging with its step-by-step explanation. RegEx Lab focuses on speed and AI assistance - get instant explanations without hovering over each character. Unlike regex101, RegEx Lab runs entirely in your browser with no data upload, making it safe for patterns containing sensitive data like API key formats or password rules.
Frequently Asked Questions
How do I test a regex pattern online?
Paste your regex pattern in the pattern field and your test string in the text area. Matches are highlighted in real-time as you type. Our regex tester supports JavaScript, Python, and PCRE regex flavors.
Can AI explain what my regex does?
Yes! Click the "Explain with AI" button to get a plain English explanation of any regex pattern. Our AI breaks down each component, explaining what characters, quantifiers, and groups do in simple terms.
What regex flags are supported?
We support all standard regex flags: g (global), i (case-insensitive), m (multiline), s (dotall), u (unicode), and y (sticky). Toggle them using the flag buttons above the pattern input.
Ready to Get Started?
Use RegEx Lab for free - no registration required.
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