Regex Tester

What is a Regex Tester?

A regex tester is an online tool that helps you build, test, and debug regular expressions. Whether you're validating user input, parsing text, or searching for patterns, seeing real-time matches makes development much faster. This tool provides instant feedback as you type, highlighting exactly what your pattern matches.

How to Use the Regex Tester

1. Enter your regex pattern — Type your regular expression in the pattern field (e.g., \d+ for digits, [a-zA-Z]+ for letters).
2. Configure flags — Check the flags you need: "g" for global (all matches), "i" for case insensitive, "m" for multiline, "s" for dotAll, "u" for unicode.
3. Enter test string — Paste or type the text you want to test against your pattern.
4. View matches instantly — See highlighted matches, their positions, and captured groups in real-time.
5. Copy your regex — Use the copy button to get your finished regex with flags (e.g., /pattern/gi).

💡 Privacy guarantee: All testing happens in your browser — your data never leaves your device.

Common Use Cases

• Form validation: Validate email addresses, phone numbers, URLs, and other user inputs using regex patterns.
• Data extraction: Extract specific parts from text like phone numbers, dates, or custom formats.
• Text parsing: Parse log files, CSV data, or structured text by identifying patterns.
• Search and replace: Build complex find-and-replace patterns for text editors or code.
• Learning regex: Experiment and see exactly what your patterns match in real-time.

Popular Regex Patterns

• Email: [\w.-]+@[\w.-]+\.\w+
• Phone (HK): (\+?852)?[569]\d8
• URL: https?://[\w.-]+(?:/[\w.-]*)*
• Date (YYYY-MM-DD): \d4-\d2-\d2
• IP Address: \d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

Key Features

• ✓ Real-time matching — See results as you type
• ✓ Visual highlighting — Spot matches easily in your test string
• ✓ Capture groups — View captured subgroups
• ✓ Pattern validation — Instant feedback on regex syntax
• ✓ Flag support — All common regex flags
• ✓ Copy to clipboard — Get your regex ready to use