The AU file format stores data in the AU format. Converting to MP3 produces a audio file that applies psychoacoustic lossy compression to remove frequencies the human ear perceives least, producing small files at acceptable audio quality. 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 MP3 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.