Which regex flavor is supported?
It targets JavaScript-style regular expressions so results align with browser and Node environments, including common flags and capture-group behavior.
Regex Tester
Test JavaScript regular expressions with live match highlighting, capture groups, and replace previews. Includes a cheatsheet and a mobile-friendly layout for quick pattern debugging.
How to use Regex Tester
- Enter a JavaScript regular expression and choose its flags.
- Paste representative text, including cases that should not match.
- Inspect highlighted matches and capture groups.
Example: The pattern \d+ with the g flag finds 12 and 34 in order 12, item 34.
Before you use the result: This tool uses JavaScript regex syntax. Patterns can behave differently in Python, Java, or PCRE; matching a string is not complete validation of its meaning.
Common questions
Can I preview replacements?
Yes. You can iterate on replace workflows and see match boundaries and capture groups with visual feedback before copying a finished pattern into code.
Does it work on mobile?
The layout is tuned for smaller screens and includes helpful reference material while you test patterns away from a desktop IDE.
Is this a free online regex tester?
Yes. It is a free browser regex playground for writing, testing, and explaining JavaScript regular expressions without installing an editor plugin.
Can I debug capture groups visually?
Yes. Live highlighting and group extraction make it easier to see what each parenthesis captured, which is often the hardest part of regex debugging.
Should I use this for production validation?
Use it to design and verify patterns quickly, then keep the same JavaScript RegExp semantics in your application tests. Extremely large inputs can still be expensive depending on the pattern.