Regex Tester

Regex Tester is a powerful free online tool for testing and debugging regular expressions with real-time match highlighting, capture group extraction, and comprehensive flag support. Whether you're a developer building validation patterns, a data analyst extracting information from text, or a student learning regular expressions, this tool provides instant visual feedback as you refine your patterns. The tool supports all standard JavaScript regex flags: global (g) for finding all matches, case insensitive (i) for ignoring letter case, multiline (m) for treating ^ and $ as line boundaries, dotAll (s) for making . match newlines, and unicode (u) for full Unicode support. As you type your pattern and test string, matches are highlighted in real-time, showing exactly what your regex captures. For each match, you can see the matched text, start and end positions, and any capture groups. The common patterns dropdown provides ready-to-use regex patterns for email validation, URL matching, phone numbers, dates, IP addresses, and more—perfect for learning or quick reference. The built-in regex cheatsheet displays essential regex syntax including character classes, quantifiers, anchors, groups, and lookarounds. Error messages explain what's wrong when your pattern has syntax issues. All processing happens entirely in your browser using JavaScript's native RegExp engine, ensuring complete privacy—your patterns and test data never leave your device. Common use cases include validating user input like emails, phone numbers, and passwords; extracting data from log files and structured text; search and replace operations; learning regular expression syntax; testing patterns before implementing them in code; and debugging complex regex for form validation. The tool handles edge cases like empty patterns, empty strings, and patterns that could cause issues. Works on all modern browsers with no installation required.