SQLlite

SQLite is a self-contained, serverless SQL database engine that runs as a highly reliable C library embedded directly inside your application.

SQLite bypasses the traditional client-server architecture by compiling directly into your application as a compact C-language library (under 700 KiB). It stores entire databases as single, cross-platform files on disk, supporting full ACID compliance and a robust SQL dialect without requiring a separate background process. This lightweight design makes it the most widely deployed database engine globally, powering local storage in billions of smartphones, web browsers, and desktop applications.

https://www.sqlite.org