Online Regex Tester

Test a regular expression against a string and see every match highlighted live, along with each match's capture groups — using JavaScript's native regex engine, the same one that runs in every browser and Node.js.

Features:

• Live highlighting: Matches are highlighted in the test string as you type.
• Capture groups: Each match's numbered groups are listed separately.
• All standard flags: Global, ignore-case, multiline, and dot-all.
• Client-side only: Your pattern and test data are never sent anywhere.

1. Common Regex Building Blocks

\d digit, \w word character, \s whitespace, . any character, * zero or more, + one or more, ? zero or one, ^ start of string, $ end of string, () capture group, [] character class.

2. Flags Explained

g (global): find every match, not just the first.
i (ignore case): match letters regardless of case.
m (multiline): ^ and $ match the start/end of each line, not just the whole string.
s (dot-all): let . match newline characters too.

3. A Worked Example

To match a simple email address: ^[\w.+-]+@[\w-]+\.[a-z]{2,}$ — one or more word characters, dots, plus, or hyphens, then @, then a domain, then a dot and a 2+ letter extension.