Regex Tools
Test regular expressions and browse common patterns.
Test a regular expression against sample text with live match highlighting and a running match count, or browse a cheatsheet of common regex patterns (email, URL, IPv4) you can copy straight into your code.
2 matches
How to use this tool
- 1Type a regular expression pattern between the slashes, and any flags (like g, i, m) in the small box on the right.
- 2Paste or type your sample text into the Test string box.
- 3Matches are highlighted live in the Matches box below, with a running match count.
Frequently asked questions
What do the flag letters mean?
g (global) finds all matches instead of just the first, i (case-insensitive) ignores letter case, m (multiline) makes ^ and $ match line boundaries instead of just the whole string, and s (dotAll) makes . match newlines too.
Why does my pattern show a syntax error?
JavaScript's regex engine is strict about unescaped special characters and unbalanced groups/brackets — for example, an unmatched ( needs a closing ). The error message names the specific problem.
Is this regex engine the same as Python or PCRE?
This uses JavaScript's native RegExp engine, which is very similar to PCRE/Python for common patterns but has some differences in advanced features like lookbehind support and named groups syntax.
Is my test text sent anywhere?
No — matching runs entirely in your browser using JavaScript's built-in regex engine. Nothing is uploaded.