Regex Tester & Validator

This regular expression extracts the file extension from a string by matching one or more word characters that immediately follow the last dot in a line. It utilizes a positive lookbehind to ensure the match is preceded by a period, and the multiline flag allows it to process multiple file paths in a single text block. It is highly useful for parsing lists of filenames, validating file types, or isolating extensions like txt, pdf, or py.