Test Regular Expressions with real-time highlighting. Runs entirely in your browser.
How to use: Type your Regex pattern in the top bar. Type or paste your test text in the box below. Matches will highlight instantly.
Regular expressions (regex) are powerful pattern-matching sequences used to search, validate, and manipulate text across virtually every programming language. Our tester provides a live environment where you write a pattern, supply test text, and instantly see matches highlighted. It shows capture groups, match positions, and total count. This immediate visual feedback dramatically accelerates developing complex patterns that would otherwise require repeated edit-compile-test cycles.
Writing correct regex is notoriously challenging—even experienced developers struggle with greedy vs. lazy quantifiers, lookbehind assertions, and nested capture groups. Our tester provides instant visual feedback, making it easy to iterate until patterns match exactly what you intend. All processing happens locally using JavaScript's native RegExp engine, ensuring test data (often production samples) is never transmitted.
The tool uses JavaScript's native RegExp (ECMAScript specification). This is compatible with most web development regex but may differ slightly from Python (PCRE), Java, or .NET.
All standard JavaScript flags: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode), and y (sticky).
Yes. Modern browsers support positive/negative lookahead (?= and ?!) and lookbehind (?<= and ?