Regex Tester & Explainer
Write, test, and debug regular expressions with real-time match highlighting, capture group inspection, and plain-English explanations.
Common Patterns
Test String
Match Highlight
Match Details
Pattern Explanation
Quick Reference
Character Classes
.Any character (except newline)\dDigit [0-9]\DNon-digit\wWord character [a-zA-Z0-9_]\WNon-word character\sWhitespace\SNon-whitespaceQuantifiers
*0 or more+1 or more?0 or 1{n}Exactly n{n,}n or more{n,m}Between n and mAnchors & Groups
^Start of string/line$End of string/line\bWord boundary(abc)Capture group(?:abc)Non-capture groupa|bAlternation (or)(?=abc)Positive lookaheadAbout Regex Testing
What is a regular expression?
Regular expressions (regex) are patterns used to match character combinations in strings. They're essential for validation, search/replace, parsing, and text manipulation.
Is this tool free?
100% free, no sign-up needed. All processing happens in your browser using JavaScript's native RegExp engine — nothing is sent to a server.
What regex flavor does this use?
This tool uses JavaScript's ECMAScript regex engine, which is the same one used in Node.js, browsers, Deno, and Bun. Flags supported: g, m, i, s, u.
Can regex patterns be dangerous?
Some patterns can cause catastrophic backtracking (ReDoS). This tool includes a timeout safety net. Avoid nested quantifiers like (a+)+ on untrusted input.
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