Regex Tester
Test and debug regular expressions with live match highlighting. Supports all JavaScript RegExp flags and named capture groups.
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About this regex tester
The regex tester gives immediate feedback for JavaScript regular expressions against sample text. It helps you see matches, test flags, and adjust patterns before placing them into validation logic, parsing scripts, or search workflows.
Common uses
- Build form validation patterns with realistic sample inputs.
- Debug capture groups for log parsing or text extraction.
- Check how global, multiline, and case-insensitive flags affect matches.
Practical notes
Test against both expected matches and inputs that should fail.
Avoid overly broad patterns in security-sensitive code because they can accept malformed input.
Frequently Asked Questions
What is a regular expression?
A regular expression (regex) is a sequence of characters that defines a search pattern. They're used for pattern matching in strings, input validation, search and replace, and data extraction.
What regex flags are supported?
g (global), m (multiline), i (case insensitive), s (dotAll - dot matches newlines), u (unicode) are all supported.
How many matches can this tool find?
The tool will find up to 500 matches. For very large inputs, consider limiting the scope of your test string.