Web Dev Tools
Regex Tester
Test and debug regular expressions instantly with live match highlighting, flag support, and detailed explanations. Perfect for validating email patterns, extracting data, and learning regex syntax.
Use Regex Tester to get instant results without uploads or sign-ups. Everything runs securely in your browser for fast, reliable output.
Your results will appear here.
About this tool
Regular expressions (regex) are powerful pattern matching tools used in programming, data validation, and text processing. However, they can be notoriously difficult to write and debug. Our Regex Tester provides instant feedback as you type, helping you perfect your patterns quickly.
Whether you're validating email addresses, extracting phone numbers from text, parsing log files, or scraping web content, regex is an essential skill. This tool supports all common regex flags including global matching, case-insensitive search, and multiline mode, making it compatible with JavaScript, Python, PHP, and most programming languages.
Unlike desktop regex tools, our online tester works in any browser with no installation required. All processing happens locally in your browser, so your sensitive data never leaves your computer. Perfect for developers, data scientists, and system administrators who need to test regex patterns quickly and securely.
The tool provides detailed match information including character positions, captured groups, and match counts, helping you understand exactly how your pattern is being applied to the test string.
Usage examples
Email Validation
Match valid email addresses
Pattern: ^[\w.-]+@[\w.-]+\.\w+$ Test: "[email protected]" Matches: ✓
Extract Phone Numbers
Find all phone numbers in text
Pattern: \d{3}-\d{3}-\d{4} (with g flag)
Test: "Call 555-123-4567 or 555-987-6543"
Matches: 2 found URL Extraction
Extract URLs from text
Pattern: https?://[\w.-]+\.[\w.-]+ (with g flag) Matches: All URLs in text
Validate Hex Colors
Match hex color codes
Pattern: ^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$
Test: "#FF5733"
Matches: ✓ Case-Insensitive Search
Find words ignoring case
Pattern: hello (with i flag) Test: "Hello World" Matches: "Hello"
How to use
- Enter your regular expression pattern in the Pattern field.
- Paste the text you want to test against in the Test String field.
- Select regex flags (g=global, i=case-insensitive, m=multiline) as needed.
- View all matches instantly with their positions and captured groups.
- The tool shows match count, positions, and detailed results.
- Use the explanation to understand how your pattern works.
Benefits
- Instant regex pattern testing with live results
- Support for all major regex flags (g, i, m, s, u, y)
- Detailed match information with positions and groups
- Compatible with JavaScript, Python, PHP, and more
- Syntax error detection and validation
- No installation required - works in any browser
- Complete privacy - all processing done locally
- Perfect for learning regex patterns
- Export-ready patterns for your code
- Test against multiple lines of text
- Debug complex patterns with match breakdown
- Essential tool for developers and data analysts
FAQs
What are regex flags and when should I use them?
Regex flags modify how patterns are matched. The "g" flag finds all matches (global), "i" ignores case, "m" enables multiline mode (^ and $ match line breaks), "s" makes dot match newlines, "u" enables Unicode, and "y" performs sticky matching. Use "g" to find all occurrences, "i" for case-insensitive searches, and "m" when working with multi-line text.
Why isn't my regex pattern matching?
Common issues include: forgetting to escape special characters (. * + ? [ ] { } ( ) ^ $ | \), incorrect flag usage (missing "g" for multiple matches), wrong anchors (^ for start, $ for end), or overly strict patterns. Use our tester to see exactly where your pattern fails.
Is this regex tester compatible with my programming language?
This tester uses JavaScript regex engine, which is similar to most languages. Small differences may exist (like lookbehind support), but 95% of patterns work identically in JavaScript, Python, PHP, Java, C#, and Ruby. Always test in your target language for production code.
What's the difference between .* and .+?
".* " matches zero or more of any character (can match empty string), while ".+" matches one or more characters (requires at least one). Use .* when the content is optional, .+ when it's required.
How do I match special characters like dots or brackets?
Escape special regex characters with a backslash: \. for literal dot, \[ for bracket, \( for parenthesis, \* for asterisk, etc. Special characters include: . * + ? [ ] { } ( ) ^ $ | \
Can I test regex for password validation?
Yes! Common password patterns include: (?=.*[A-Z]) for uppercase, (?=.*[a-z]) for lowercase, (?=.*\d) for digits, (?=.*[@$!%*?&]) for special chars, and {8,} for minimum length. Combine these lookaheads for strong password validation.
What are capturing groups in regex?
Capturing groups use parentheses ( ) to extract specific parts of a match. For example, (\d{3})-(\d{3})-(\d{4}) captures three groups from a phone number. Use (?:...) for non-capturing groups when you need grouping but not extraction.
Is my regex test data private?
Absolutely! All regex testing happens entirely in your browser using JavaScript. No data is sent to any server. Your test strings, patterns, and results remain completely private on your computer.
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