The MPEG-1 Audio Layer III format applies psychoacoustic lossy compression to remove frequencies the human ear perceives least, producing small files at acceptable audio quality. Converting to M4A produces a audio file that stores AAC-encoded audio in an MPEG-4 container, the standard audio format produced by iTunes and Apple devices. 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 M4A the practical choice when the destination system requires it or when the target format offers better compatibility or compression. 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.