Regex Validator & Tester
Test and debug regular expressions with live match highlighting, capture groups, and instant validation feedback.
Our Regex Validator is a powerful free tool for testing and debugging regular expressions with live match highlighting, capture group extraction, and instant error detection. Perfect for developers working with JavaScript, Python, PHP, or any language that uses regex patterns.
Frequently Asked Questions
What is a regex validator?
A regex validator is a tool that tests regular expression patterns against sample text to verify they work correctly. It shows matches, highlights text, extracts capture groups, and detects syntax errors—essential for debugging regex before using it in production code.
How do I test a regex pattern?
Enter your regex pattern in the pattern field, add test text, and configure flags (global, case-insensitive, multiline). The validator instantly shows matches with yellow highlighting, displays match positions, and extracts capture groups for detailed analysis.
What are regex flags?
Flags modify regex behavior: 'g' (global) finds all matches instead of stopping at the first, 'i' (case-insensitive) ignores letter case, and 'm' (multiline) treats ^ and $ as line boundaries instead of string boundaries.
Can I see capture groups in matches?
Yes! When your pattern includes capture groups like (\d+) or ([a-z]+), the validator displays each group's content with its index ($1, $2, etc.) below each match, helping you verify your grouping logic works correctly.
Does this work with all programming languages?
The validator uses JavaScript regex engine, which is similar to Python, PHP, and Java but has minor differences. Most patterns work across languages, but always test in your target environment for production use, especially with advanced features like lookbehinds.
How is this different from the regex generator?
The Regex Generator helps BUILD patterns with templates and explanations, while the Validator helps TEST existing patterns with detailed match highlighting and capture groups. Use the generator to create, then the validator to debug and refine your regex.