Regex Tester

Regular expressions (regex) are powerful pattern-matching sequences used across virtually every programming language and text editor. They let you search, validate, and extract data from strings using concise, expressive syntax. From validating email addresses and phone numbers to parsing log files and transforming text, regex is an indispensable tool in every developer's toolkit. However, writing correct patterns can be tricky, which is why a real-time tester is essential for iterating quickly.

This tool lets you type a regex pattern and immediately see which parts of your test string are matched. Matches are highlighted directly in the text so you can visually verify the pattern's behavior. You can toggle the global flag to find all matches or just the first, the case-insensitive flag to ignore letter casing, and the multiline flag to make the caret and dollar anchors match at line boundaries instead of only the start and end of the entire string. Each match displays its index position and any captured groups.

Common regex use cases include form validation (email, URL, and date patterns), search-and-replace operations in code editors, log analysis with capture groups to extract timestamps or error codes, and data scraping where patterns identify structured content within unstructured text. This tool handles regex errors gracefully, displaying clear messages for malformed patterns so you can correct mistakes without guessing. All processing runs locally in your browser for maximum speed and privacy.