Regex Tester — Free Online Tester
Test regular expressions with live matching
All processing happens locally. No data is sent to any server.
Regular expressions (regex) are powerful pattern-matching tools used in programming, data validation, and text processing. Our Regex Tester lets you write and test patterns in real-time with instant visual feedback. Enter your regex pattern and test string to see matches highlighted in real-time. Toggle flags like global (g), case-insensitive (i), multiline (m), and dotAll (s) to modify matching behavior. The matches table shows each match with its index, groups, and named captures — making it easy to verify your pattern works correctly before using it in your code or configuration files. Use the common patterns library to quickly load frequently used regex patterns for emails, URLs, IPs, phone numbers, dates, and more. This saves time when you need standard patterns for validation or extraction tasks. You can also copy patterns directly to your clipboard for use in your code. The tool supports both JavaScript regex syntax and common regex flavors used in Python, Go, and other languages for cross-platform compatibility. All matching happens in your browser — your data never leaves your device. This makes it safe to use with sensitive data like API responses or confidential text that needs pattern matching. For related text processing, try our [Diff Viewer](/tools/diff-viewer) to compare text changes, or use our [Cron Expression Parser](/tools/cron-parser) to validate scheduling patterns.
FAQ
What is a regular expression?
A regular expression (regex) is a sequence of characters that defines a search pattern. It's used for pattern matching within strings, commonly for validation, search, and replace operations.
What do the flags mean?
g (global) finds all matches, i (case-insensitive) ignores case, m (multiline) treats each line separately, and s (dotAll) allows . to match newlines.
How do I capture groups?
Use parentheses () in your pattern to create capture groups. Named groups use the syntax (?<name>pattern). Groups appear in the matches table below the input.
Is my data safe?
Yes. All regex testing happens in your browser. Your data never leaves your device.