The HEIF file format stores data in the HEIF format. Converting to SK1 produces a document file that stores data in the SK1 format. This conversion changes the file's encoding, compression method, and supported feature set. Text content, headings, and basic formatting are transferred; complex features such as macros or embedded objects may not translate fully. This makes SK1 the practical choice when the destination system requires it or when the target format offers better compatibility or compression. 1converter runs this conversion on the server: your file is uploaded encrypted over HTTPS, converted using trusted open-source libraries, and the output is held for 24 hours before automatic deletion.