Regex Tester
Test and debug regular expressions in real-time with match highlighting, capture groups, and detailed results. No signup required.
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What is Regex Tester?
Regex Tester is an interactive tool for testing and debugging regular expressions (regex) in real-time. It highlights matches instantly, shows capture groups, explains pattern syntax, and supports multiple regex flavors including JavaScript, Python, and PCRE.
Key Benefits
- Real-time pattern matching
- Capture group highlighting
- Pattern explanation
- Multiple regex flavors
Common Use Cases
- •Pattern development
- •Text extraction
- •Form validation
- •Log parsing
- •Data cleaning
How to Test Regular Expressions
- Enter your regex pattern: Type your regular expression pattern in the pattern field. Use standard regex syntax—no need to add delimiters like /pattern/.
- Add test text: Paste or type the text you want to test against in the test string area. The tool highlights matches instantly.
- Set regex flags: Toggle flags as needed: g (global/find all), i (case-insensitive), m (multiline), s (dotall), u (unicode).
- Analyze results: View highlighted matches, capture groups, and match details. Use the explanation feature to understand what each part of your pattern does.
Key Features
- Real-time pattern matching and highlighting
- Support for all regex flags (g, i, m, s, u)
- Capture group visualization
- Match details with index positions
- Pattern explanation and breakdown
- Common pattern library
Frequently Asked Questions
How do I test a regular expression online?
Enter your regex pattern in the pattern field and your test text below. Matches are highlighted in real-time. You can toggle flags like case-insensitive (i), global (g), and multiline (m). Capture groups are shown separately for easy debugging.
What do regex symbols like ^, $, *, + mean?
^ matches the start of a string. $ matches the end. * means 0 or more occurrences. + means 1 or more. ? means 0 or 1 (optional). . matches any character except newline. \d matches digits. \w matches word characters (letters, digits, underscore).
How do I match an email address with regex?
A basic email pattern is: ^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,}$ . However, email validation with regex is notoriously complex—the full RFC 5322 spec is nearly impossible to capture. For production, use a simpler pattern and verify with confirmation emails.
Why is my regex not matching?
Common issues: forgetting to escape special characters (\. instead of .), missing the global flag (g) for multiple matches, wrong anchors (^ and $), greedy vs lazy quantifiers (* vs *?), and not accounting for whitespace or line endings.
In-depth guide
Complete Guide to Regex Tester: Master Regular Expressions Online
Read the full guide →
In-depth guide
Regex for Beginners: 10 Patterns Every Developer Needs
Read the full guide →
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