Regex Editor & Tester

This regular expression matches standard email addresses by capturing the local part with alphanumeric characters and an optional separator (underscore, dot, or hyphen), followed by an '@' symbol and a domain name. It uses a lookbehind assertion to ensure the email is preceded by either whitespace or the start of a line, preventing partial matches within larger invalid text. It is particularly useful for extracting email addresses from documents or validating basic email formats.