M4A is a audio format: it stores AAC-encoded audio in an MPEG-4 container, the standard audio format produced by iTunes and Apple devices. MP3 is a audio format 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. Converting between these two formats is common when the source application does not support MP3 natively or when the target platform only accepts MP3. 1converter processes this conversion server-side using open-source tools. Files are transferred over HTTPS, converted on secure cloud servers, and automatically deleted after 24 hours.