SQLite3 is a popular serverless SQL engine, implemented as a library to be used within other applications. It keeps its databases as regular disk files.
Every database file is segmented into pages. First page (starting at the very beginning) is special: it contains a file-global header which specifies some data relevant to proper parsing (i.e. format versions, size of page, etc). After the header, normal contents of the first page follow.
Each page would be of some type, and generally, they would be
reached via the links starting from the first page. First page type
root_page) is always "btree_page".
This page hosts a formal specification of SQLite3 database file using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.