Regex Tester

How to Use the Regex Tester

1. Enter your regular expression pattern in the pattern field, or click a quick-insert button to load a common pattern (email, URL, phone, IP, date, hex color).
2. Toggle flags as needed: g for global matching, i for case-insensitive, m for multiline, and s for dotAll mode.
3. Paste or type your test string in the text area below. Matches are highlighted in real time as you type.
4. Review the match results panel showing match count, index positions, matched values, and capture group contents.
5. Iterate on your pattern until all intended matches are captured. If the regex is invalid, an error message appears immediately.

Common Use Cases

• Validating email addresses, URLs, and phone numbers before implementing patterns in production code.
• Debugging data extraction patterns for web scraping, log parsing, or CSV processing pipelines.
• Testing input validation rules for forms, API endpoints, and configuration files.
• Learning regex syntax by experimenting with capture groups, quantifiers, and character classes in a visual environment.
• Building search-and-replace patterns for code refactoring across large codebases.
• Verifying security patterns for detecting SQL injection attempts, XSS payloads, or malformed input.

Frequently Asked Questions

Which regex engine does this tool use?

The tester uses JavaScript's built-in RegExp engine, which follows the ECMAScript specification. Patterns that work here will work in Node.js, browsers, and any JavaScript runtime. Note that some features available in PCRE (Perl-compatible) engines, like lookbehinds in older browsers, may have limited support.

Can I test multiline patterns?

Yes. Enable the m (multiline) flag so ^ and $ match the start and end of each line rather than the entire string. Enable the s (dotAll) flag if you need . to match newline characters.

How do capture groups work?

Wrap part of your pattern in parentheses to create a capture group, e.g., (\d{3})-(\d{4}). The match results panel shows each group's value separately, letting you extract specific portions of matched text. Use the Diff Checker to compare regex outputs, or explore our web development services for custom data processing solutions.