> Acorn’s native file format is used to losslessly store layer data, editable text, layer filters, an optional composite of the image, and various metadata. Its advantage over other common formats such as PNG or JPEG is that it preserves all this native information without flattening the layer data or vector graphics.
As I've mentioned, this is a good use case for SQLite as a container. But ZIP would work equally well here.
https://shapeof.com/archives/2025/4/acorn_file_format.html
The author notes that an advantage is that other programs can easily read the file format and extract information from it.