The MPEG-4 Audio format stores AAC-encoded audio in an MPEG-4 container, the standard audio format produced by iTunes and Apple devices. Converting to AU produces a document file that stores data in the AU format. This conversion changes the file's encoding, compression method, and supported feature set. Metadata such as creation date and embedded colour profiles is preserved where the target format supports it. This makes AU the practical choice when the destination system requires it or when the original format is not supported by the target application. 1converter runs this conversion on the server: your file is uploaded encrypted over HTTPS, converted using trusted open-source libraries, and the output is held for 24 hours before automatic deletion.