Regex Tester & Validator

Matches text from the start of each line up to (but not including) a colon, using a lookahead to require at least one character after the colon. Ideal for extracting keys from key-value pairs in config files, HTTP headers, YAML-like structures, or Python dictionary output. The multiline flag (^ matches at each line start) combined with global matching enables processing multiple key:value lines at once.