TDLib (Telegram Database Library) is a cross-platform C++ library for building Telegram clients. It implements the full MTProto protocol stack, including encryption, transport (TCP, HTTP, TLS), and proxy support (SOCKS5, HTTP). The library manages all Telegram data types (messages, users, dialogs, files, etc.) with local persistence via SQLite and a custom binary log for crash-safe state. It provides a clean JSON-based API (td_json_client) for usage from any language, along with native bindings for Java, .NET, C, and more. The architecture is actor-based (tdactor), enabling high concurrency without explicit thread management. The codebase also includes code generation tools that produce serialization code from Telegram's Type Language (TL) schema, ensuring type safety and protocol compliance.