AU is a document format: it stores data in the AU format. FLAC is a audio format that applies lossless compression to PCM audio, preserving the original waveform exactly while reducing file size by 40-60% versus WAV. 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 FLAC natively or when the target platform only accepts FLAC. 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.