While Fossil uses SQLite for underlying storage (instead of the filesystem directly) and various support infrastructure, its actual format is not based on SQLite: https://fossil-scm.org/home/doc/trunk/www/fileformat.wiki

It's basically plaintext. Even deltas are plaintext for text files.

Reason: "The global state of a fossil repository is kept simple so that it can endure in useful form for decades or centuries. A fossil repository is intended to be readable, searchable, and extensible by people not yet born."