Is it flavourful or flavorful?
It depends on where your audience is located. In British English, the correct spelling is flavourful, and in American English, it is flavorful.
The “-our” or “-or” difference also holds true for the noun, verb, and adjective flavour/flavor, and all the forms of the verb (e.g., flavouring/flavoring).
The QuillBot Grammar Checker will help you to ensure that you have the correct spelling of flavour or flavor.