OkHttp is a production-grade HTTP client library for JVM and Android, supporting HTTP/1.1, HTTP/2, WebSockets, Server-Sent Events, TLS/SSL, DNS over HTTPS, content compression (gzip, brotli, zstd), caching, cookies, and authentication. It is designed for efficiency with connection pooling, multiplexing, and async execution. The architecture is a multi-module Kotlin/Gradle project with a core library (okhttp) and optional extensions (brotli, zstd, sse, coroutines, logging, DNS over HTTPS, TLS utilities). It uses an interceptor chain pattern for request/response processing, with application interceptors and network interceptors. Platform abstraction handles JVM vs Android differences for TLS, DNS, and sockets. Key entry points include OkHttpClient, Request, Response, Call, Interceptor, EventListener, WebSocket, and EventSource. External dependencies include Okio (I/O library), Kotlin stdlib, and optional TLS providers (Conscrypt, BouncyCastle, OpenJSSE). The library is extensively tested with unit tests, integration tests, and Android device tests.