Regex Editor & Tester

This regex matches the literal string 'box' only when it is immediately followed by '-shadow', without consuming the '-shadow' part. The positive lookahead (?=-shadow) is a zero-width assertion that verifies the suffix exists but keeps it out of the match itself. A common use case is matching 'box' in CSS 'box-shadow' properties while excluding the hyphenated suffix, useful in token highlighting or CSS preprocessing. The g flag finds all occurrences and m enables line-by-line matching.