AU is a document format: it stores data in the AU format. OPUS is a audio format that stores data in the OPUS format. 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 OPUS natively or when the target platform only accepts OPUS. 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.