Regex Tester JavaScript — Test Regular Expressions Online

Regex Tester JavaScript A regex tester for JavaScript lets you write and validate regular expressions with live feedback — no console.log loops, no Node.js terminal, no guessing. Paste your pattern and test string, and see exactly which parts match, which groups capture, and where the regex fails. This guide covers JavaScript regex syntax, the most useful patterns, and how to avoid the common traps that make regex debugging painful. JavaScript Regex Basics JavaScript has built-in regular expression support via the RegExp object and regex literals: // Regex literal syntax (preferred) const pattern = /hello/i ; // Constructor syntax (for dynamic patterns) const term = " hello " ; const dynamic = new RegExp ( term , " i " ); // Test if a string matches console . log ( pattern . test ( " Hello World " )); // true // Find all matches console . log ( " Hello hello " . match ( /hello/gi )); // ["Hello", "hello"] Regex Flags in JavaScript Flags change how the pattern behaves: Flag Name Effect