Free online regex tester to test and debug regular expressions in real-time. Enter your pattern and test text, see all matches highlighted instantly with capture groups. Supports flags like g, i, m, s, u. All processing happens in your browser.
Enter a pattern and test text to see matches
Testing and debugging regular expressions is easy with our real-time regex tester. Here's how to use it:
Regular expressions are powerful but can be tricky to get right. A regex tester is essential whenever you're working with pattern matching:
Regular expressions (regex) are patterns used to match character combinations in strings. They're incredibly powerful for text processing, validation, and extraction. Common elements include: literal characters (match themselves), metacharacters like . (any character), * (zero or more), + (one or more), ? (optional), \d (digit), \w (word character), \s (whitespace), anchors like ^ (start) and $ (end), character classes like [a-z], and groups with (). Understanding these building blocks lets you create patterns for virtually any text-matching task.
The regex tester runs entirely in your browser using JavaScript's built-in RegExp engine. As you type your pattern and test text, it re-evaluates the regex in real-time, highlighting all matches in your input text with different colors. Each match is also displayed below with its position (start and end index) and any captured groups. Nothing is sent to any server - your data stays private on your device.
This tester uses JavaScript's RegExp syntax, which supports most standard regex features including: literal characters, metacharacters (., *, +, ?, |, ^, $), character classes ([a-z], [^abc], \d, \w, \s), quantifiers ({3}, {2,5}), groups and backreferences ((abc), \1), lookahead/lookbehind ((?=), (?!), (?<=), (?<!)), and flags (g, i, m, s, u). Some advanced PCRE features like atomic groups and recursion are not supported in JavaScript.
If no matches are found, check your pattern carefully: make sure you haven't missed a closing bracket, parenthesis, or backslash. Verify your flags - for example, forgetting the 'i' flag when your pattern uses uppercase but your text is lowercase. Also check if you need the 'm' flag when using ^ or $ anchors on multi-line text. Try simplifying your pattern to isolate the issue.
Each match is highlighted with a unique color to help you distinguish between multiple matches visually. When you click on a match in the result list below, the corresponding highlight in the text will be scrolled into view, making it easy to locate specific matches in long text.
This tool focuses on matching and visualization, but the captured group information shown below each match is exactly what you'd use in a replacement pattern. In JavaScript, captured groups are referenced as $1, $2, etc. in replacement strings. Use this tester to verify your groups are capturing the right content before applying them in your actual code.
No, absolutely not. Everything happens entirely in your browser. Your regex pattern and test text never leave your device. This means you can safely test patterns against sensitive data like passwords, API keys, or personal information without any privacy concerns. As soon as you refresh or leave the page, everything is gone.
Greedy quantifiers (*, +) match as much as possible, while lazy quantifiers (*?, +?) match as little as possible. For example, on the text '<div>Hello</div>', the pattern <.*> would match the entire string (greedy), while <.*?> would match '<div>' only (lazy). Use lazy quantifiers when you want the shortest possible match that still satisfies the pattern.