The EazyDraw native file format is an open non-proprietary public format. The data content is in a human/machine English readable text. We use macOS's XML Parameter List (pList) dictionary based format. This is the best archive format, since it is human readable text a corruption can be easily found, corrected or isolated allowing recovery of a damaged file.
Alternatively file data may be saved in a raw binary format which is more compact, may be quicker to open and save. This is the best format if the drawing contains bitmap images, or for email attachments.
The third native format is a macOS bundle. Bundles are actually just special purpose folders. The bundle contains one drawing file for each Layer's graphics and a separate file for the information needed to set up the display window and determine which layers are needed for quick display. This format saves system resources by not reading (or writing) layers that are not in immediate use, or layers that have not changed since the last save. This architecture allows your system, which likely has multiple CPU's to assign different CPU's the task of reading and writing individual layers. Most of todays Macs are so fast and efficient that little gain in performance is seen, although those with solid state drives (mac-air's) can be very responsive using this mode.
An XML style data file is much larger than a corresponding binary file. Both forms are provided by EazyDraw. It is somewhat counter intuitive, but the larger text based XML form should always be used for long term archival. If data is lost or corrupted, a binary file is probably lost completely with little hope of recovery. While a corrupted text based file can usually be recovered with a little patience and a good text editor.