SQLite

SQLite is a C-language library: a self-contained, serverless, zero-configuration SQL database engine embedded directly into the application process.

SQLite is the world's most deployed database engine, functioning as a compact, C-language library (under 900KiB with all features) that eliminates the need for a separate server process. It operates as a serverless, zero-configuration system, storing the entire database (up to 281 terabytes) in a single, cross-platform file. This architecture makes it ideal for countless applications: it is built into all major mobile phones, web browsers, and desktop operating systems. The engine guarantees high reliability, supporting full ACID transactions, and its source code is freely available in the public domain for any use.

https://www.sqlite.org