Regex Tester
Test regular expressions against text, inspect matches and debug patterns directly in your browser.
About Regex Tester
Test regular expressions against text, inspect matches and debug patterns directly in your browser. NeroTool keeps this workflow simple and browser-based. Where supported, processing happens locally in your browser.
How to use this tool
Enter a pattern and any flags such as g or i, paste sample text, then select Test regex. Every match found in the text is listed below.
Greedy vs. lazy matching
A greedy quantifier like * or + tries to match as much text as possible before backtracking, which can make a pattern span further than intended. A lazy quantifier, written with a trailing ?, matches as little as possible instead — useful when a test unexpectedly matches too much text.
Privacy
This tool is designed to work in your browser. NeroTool does not require an account for this workflow.
Frequently asked questions
Why is my regex matching more text than expected?
This usually happens with a greedy quantifier; switching to a lazy quantifier or narrowing the character class often fixes it.
What do the flags like g and i do?
The g flag finds all matches instead of stopping at the first one, and the i flag makes the match case-insensitive.
Can I test capture groups?
Yes, the tool highlights matches and shows any groups captured with parentheses in your pattern.
Is my text uploaded anywhere?
The tester runs in your browser, so the pattern and text you enter are not intentionally sent to a NeroTool server.