Regular Expression Tester
Build and test regular expressions with live match highlighting. Type a pattern, add flags, provide sample text, and watch every match light up as the pattern takes shape.
How to use the RegEx Tester
- Enter your regex pattern in the expression field.
- Toggle flags such as global and case-insensitive as needed.
- Paste sample text into the test area.
- Review highlighted matches and tweak the pattern until it captures exactly what you want.
When the RegEx Tester is useful
- Writing validation patterns for emails, phone numbers, or usernames.
- Debugging a regex that matches too much or too little in production data.
- Learning regex by experimenting with immediate visual feedback.
- Testing extraction patterns before embedding them in code.
How the RegEx Tester works
The tester applies your pattern with the selected flags and highlights every match directly inside the sample text, with match boundaries clearly visible. Common modifiers, global search, case-insensitivity, and multiline mode, are one click away. Because patterns you are testing often reflect private data formats, the entire engine runs client-side with nothing transmitted.
Limits to keep in mind
Regex behavior can differ subtly between engines; a pattern validated here in JavaScript semantics may need tweaks for PCRE or POSIX environments.
Frequently asked questions
What does the g flag do?
It makes the search continue past the first match, returning every occurrence in the text.
Can I test capture groups?
Yes, groups are highlighted so you can see exactly what each portion of your pattern captures.
Is my sample text uploaded?
No. Matching happens locally, so proprietary data used for testing stays on your machine.
Last reviewed: October 2026.