MPEG-4 Audio (M4A) stores AAC-encoded audio in an MPEG-4 container, the standard audio format produced by iTunes and Apple devices. Matroska Video (MKV) stores video, audio, subtitles, and chapters in an open-standard container that supports virtually every codec. This wraps the audio track in a video container, which some platforms require for upload. Metadata such as creation date and embedded colour profiles is preserved where the target format supports it. The result is a standard MKV file readable by any compatible application. 1converter handles M4A-to-MKV conversion server-side: files are uploaded over HTTPS, processed on isolated cloud infrastructure, and the converted output is available for download for 24 hours before automatic deletion. No account is required for standard conversions.