SK1 is a document format: it stores data in the SK1 format. HEIC is a image format that applies H.265 (HEVC) intra-frame compression achieving roughly twice the efficiency of JPEG at equal visual quality, used natively by Apple devices. This renders each page as a raster image, making the content viewable without a document reader. Each page is rendered at the specified DPI and saved as a separate image; text in the output is no longer selectable. Converting between these two formats is common when the source application does not support HEIC natively or when the target platform only accepts HEIC. 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.