Regex Tester
Test and debug regular expressions with real-time match highlighting.
About Regex Tester
The most powerful free online regex tester. Test regular expressions against input text with real-time match highlighting, capture groups, and detailed match info. Supports all JavaScript regex flags (g, i, m, s, u). Includes a library of common patterns.
Real-time regex testing with visual match highlighting — see exactly which characters match as you type. Supports all JavaScript regex flags. Shows individual match groups so you can verify capture groups are working correctly. Far faster than testing regex in browser console.
How to Use Regex Tester
- 1Enter your regular expression in the Pattern field (without surrounding slashes).
- 2Add flags as needed in the Flags field: 'g' for global match, 'i' for case-insensitive, 'm' for multiline.
- 3Type or paste your test string in the Test String area.
- 4All matches are highlighted in real-time — no need to click 'test'.
- 5View individual matches listed below the test string, showing each captured match.
Key Features
Use Cases for Regex Tester
Form Input Validation
Test email, phone number, URL, and password validation patterns before adding them to production code. Verify your regex handles edge cases: international phone formats, subdomains, special characters in passwords.
Log File Parsing
Extract structured data from unstructured log files. Build patterns to parse timestamps, IP addresses, error codes, and messages from Apache, Nginx, or custom application logs.
Data Cleaning & Transformation
Build search-and-replace patterns for data processing pipelines. Test patterns that extract pricing, dates, addresses, or product codes from messy scraped or imported data.
String Manipulation in Code
Test regex patterns before embedding them in JavaScript, Python, or other code. Catch edge cases in a visual interface rather than through console.log debugging loops.
Always test your regex against edge cases, not just the happy path. If you're validating emails, test: user@domain.co.uk, user+tag@domain.com, user@sub.domain.com, and invalid inputs like user@domain, @domain.com, and user@.com. Your pattern needs to handle all of them correctly.
Frequently Asked Questions
What is a regular expression?
A regular expression (regex) is a pattern used to match character combinations in strings. It's used in search, validation, and text manipulation across all programming languages.
How do I test my regex?
Enter your pattern in the Pattern field. Your test string below will show matches highlighted in real-time as you type. Enable flags like "g" for global match or "i" for case-insensitive.
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