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. AAC is a audio format that uses psychoacoustic lossy compression similar to MP3 but with improved efficiency, delivering better quality at the same bitrate. 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 AAC natively or when the target platform only accepts AAC. 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.