Regex Tester

Test regular expressions with live match highlighting, match positions, and capture groups.

Deep Dive

Test regular expressions against sample text in real time with live match highlighting. Supports all JavaScript regex flags (g, i, m, s, u), named capture groups, and displays each match's index and captured groups. No data leaves your browser.

Use Cases

Building and testing an email validation regex

Extracting dates or phone numbers from a block of text

Debugging a complex search-and-replace pattern

Learning regex syntax interactively

Examples

Match email addresses

Input

Contact us at hello@karuvilab.com or support@example.org

Output

Matches: hello@karuvilab.com, support@example.org

Extract digits

Input

Order #4521 ships in 3 days

Output

Matches: 4521, 3

Frequently Asked Questions

Which regex flavor does this use?

JavaScript's built-in RegExp engine. Most common patterns are compatible, but features like lookbehinds require a modern browser (Chrome 62+, Firefox 78+).

Why does my regex match nothing?

Check that special characters (., *, +, ?, (, )) are escaped with a backslash if you want them treated literally.

What are flags and when do I use them?

g finds all matches (not just the first), i ignores case, m makes ^ and $ match line boundaries, s makes . match newlines.

Can I use named capture groups?

Yes. Use (?<name>...) syntax. Named groups are displayed alongside numeric groups in the match list.