Godot Engine – Multi-platform 2D and 3D game engine

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

Emscripten: An LLVM-to-WebAssembly Compiler

The open-source database for the realtime web.

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)

Filament is a real-time physically based rendering engine for Android, iOS, Windows, Linux, macOS, and WebGL2

Cross-platform, graphics API agnostic, "Bring Your Own Engine/Framework" style rendering library.

A fast JSON parser/generator for C++ with both SAX/DOM style API

A fast multi-producer, multi-consumer lock-free concurrent queue for C++11

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.

Industry-standard navigation-mesh toolset for games

Minimalistic GUI library for OpenGL

A tool for use with clang to analyze #includes in C and C++ source files

Tools for tracing OpenGL, Direct3D, and other graphics APIs

Mesh parameterization / UV unwrapping library

EntityX - A fast, type-safe C++ Entity-Component system

A small, portable and extensible C++ 3D coding framework

CodeXL is a comprehensive tool suite that enables developers to harness the benefits of CPUs, GPUs and APUs.

A lightweight embeddable flash player.

An Experimental Entity-Component-Based Multithread Game Engine.