How to Use a Regex Tester

A regex tester shows which parts of your text match a regular expression pattern.

Open Regex tester

What regex is useful for

Regex can find email addresses, phone numbers, product codes, hashtags and mentions.

A good pattern speeds up validation, cleanup and log analysis.

Is regex enough for validation?

It helps check format but cannot alone prove that an email, URL or domain is real.

What is catastrophic backtracking?

It is excessive work caused by poorly designed repetition on certain inputs.