Is molding or moulding correct?

Both molding and moulding are considered entirely correct and acceptable spellings of the exact same word, with their primary distinction lying in regional spelling conventions rather than grammatical accuracy. Moulding with the traditional letter u is the standard spelling utilized extensively throughout the United Kingdom, Australia, New Zealand, Canada, and other nations following British Commonwealth English guidelines. Conversely, molding without the u is the established standard spelling preferred across the United States within American English dictionaries, building supply industries, and architectural literature. Because both variations refer to identical decorative millwork, manufacturing processes, and shaping concepts, writers and contractors can use either form with confidence, though matching the spelling convention of your specific geographic region is always best practice for professional consistency.