Regex Editor & Tester

This regex extracts the value of the utm_source query parameter from a URL string into a named capture group called 'utm_source'. It uses a positive lookbehind to match text immediately after 'utm_source=' and a lookahead to stop at an ampersand, whitespace, or end of line, making it robust for URLs embedded in text or logs. It's commonly used in web analytics, log parsing, and marketing attribution to identify traffic sources.