okhttp

OkHttp is a library for making HTTP network requests from Java, Kotlin, and Android applications. HTTP is the protocol used to transfer data over the web — whenever your app fetches data from an API, downloads an image, or posts a form, it makes an HTTP request. The standard networking tools built into the Java and Android platforms work but have awkward APIs and lack many modern features. OkHttp provides a cleaner, more capable alternative.

It is efficient by default in several important ways. It supports HTTP/2, a newer version of the protocol that allows multiple requests to the same server to share a single connection instead of opening a new one for each request, which significantly reduces latency. It uses connection pooling even for older HTTP/1.1 connections, automatically compresses responses using GZIP to reduce download sizes, and caches responses so repeat requests for the same data skip the network entirely. It handles real-world network reliability: if a server has multiple IP addresses (common for load-balanced services), OkHttp tries them in order on failure. It supports modern TLS security features including TLS 1.3 and certificate pinning. The API uses a builder pattern common in Java/Kotlin where you chain method calls to configure a request before sending it, and it supports both synchronous (blocking) and asynchronous (callback-based) request modes.

You would use OkHttp in any Java or Kotlin application — including Android apps — that makes HTTP calls to web APIs, downloads files, or communicates with a backend server. It is the default HTTP client underlying many other popular Android libraries. It also includes a MockWebServer module for writing tests that simulate a real HTTP server without making actual network calls. The library is written in Kotlin and distributed via Maven Central.