Dear ImGui: Bloat-free Graphical User interface for C++ with minimal dependencies

JSON for Modern C++

C++ based gRPC (C++, Python, Ruby, Objective-C, PHP, C#)

Emscripten: An LLVM-to-WebAssembly Compiler

FlatBuffers: Memory Efficient Serialization Library

A modern formatting library

A brief computer graphics / rendering course

A modern, C++-native, test framework for unit-tests, TDD and BDD - using C++14, C++17 and later (C++11 support is in v2.x branch, and C++03 on the Catch1.x branch)

Simple, secure & standards compliant web server for the most demanding of applications

Seamless operability between C++11 and Python

ESP8266 core for Arduino

ArduPlane, ArduCopter, ArduRover, ArduSub source

The POCO C++ Libraries are powerful cross-platform C++ libraries for building network- and internet-based applications that run on desktop, server, mobile, IoT, and embedded systems.

Main gperftools repository

A collection of C++ HTTP libraries including an easy to use HTTP server.

Crow is very fast and easy to use C++ micro web framework (inspired by Python Flask)

C++ Requests: Curl for People, a spiritual port of Python Requests.

ESP8266 WiFi Connection manager with web captive portal

Guidelines Support Library

Official doxygen git repository

header only, dependency-free deep learning framework in C++14

Bloaty: a size profiler for binaries

A brief computer graphics / rendering course

Lightweight and modular C++11 graphics middleware for games and data visualization

The code base of SuperTuxKart

Extremely simple yet powerful header-only C++ plotting library built on the popular matplotlib

Range library for C++14/17/20, basis for C++20's std::ranges

Embedded Scripting Language Designed for C++

Fast Library for Approximate Nearest Neighbors

An Arduino library that adds one or more joysticks to the list of HID devices an Arduino Leonardo or Arduino Micro can support.