validators\FileValidator $mimeTypes

A list of file MIME types that are allowed to be uploaded. This can be either an array or a string consisting of file MIME types separated by space or comma (e.g. "text/plain, image/png"). The mask with the special character * can be used to match groups of mime types. For example image/* will pass all mime types, that begin with image/ (e.g. image/jpeg, image/png). Mime type names are case-insensitive. Defaults to null, meaning all MIME types are allowed.

See also $wrongMimeType for the customized message for wrong MIME type.