Regex Tester
Test regular expressions with live match highlighting
Enter a pattern to see matches
Enter a replacement pattern to see result
Frequently Asked Questions
What is a Regex Tester?
It's a tool that allows you to write and test Regular Expressions against a sample text to see if they match and what they capture.
Which Regex flavor do you support?
Our tester uses the standard JavaScript (ECMAScript) regex engine, which is compatible with most web development needs.
What are Regex 'Flags'?
Flags are modifiers like `g` (global), `i` (case-insensitive), and `m` (multiline) that change how the engine searches for matches.
Can the tool explain my Regex?
Yes, we providing a breakdown of each part of your expression (like quantifiers, anchors, and character classes) to help you understand it better.
How do I capture groups in Regex?
Use parentheses `(...)` to create a capturing group. Our tool will highlight each specific group match in the sample text.
Is my regex saved anywhere?
No. Everything happens in your browser session. We do not store your expressions or sample data on our servers.
Does it support negative lookaheads?
Yes, as long as the browser's JavaScript engine supports them (which most modern browsers do), you can use advanced lookahead/lookbehind patterns.
Can I test replacement strings here too?
Yes, there is a separate section to test how your Regex would perform a 'Find and Replace' operation on the text.
Are there common Regex patterns available?
Yes, we provide a cheat sheet and common snippets for email, URL, and phone number validation for quick reference.
Is RegEx hard to learn?
It has a steep learning curve, but tools like this tester make it much easier by providing instant visual feedback as you type.