yhirose/cpp-httplib

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library.

The library addresses the need for lightweight, easy-to-integrate HTTP communication in C++ applications. It works by providing a single header file that developers include directly in their code, eliminating complex build dependencies. The implementation supports both server and client modes with SSL/TLS encryption through multiple backends including OpenSSL, Mbed TLS, and wolfSSL. Additional capabilities include WebSocket support, Server-Sent Events, and a Stream API for flexible request and response handling.

Developers should adopt this library if they need straightforward HTTP functionality in a C++ project without heavyweight dependencies. It suits applications requiring basic HTTP/HTTPS communication where simplicity and ease of integration matter more than advanced features. The library explicitly uses blocking socket I/O, making it unsuitable for projects requiring non-blocking asynchronous networking. It supports only HTTP/1.1, so applications needing HTTP/2 or HTTP/3 should look elsewhere.

Development activity shows that CI includes only basic compile checks rather than functional or security testing. Custom certificate verification through callbacks and mutual TLS support are available for applications requiring advanced authentication. The library provides detailed SSL error information through separate methods for TLS-level and backend-specific error codes. BoringSSL is supported on a best-effort basis with known behavioral differences from OpenSSL, including C++14 requirement and SAN-only hostname verification.