Boost

Boost provides peer-reviewed, portable C++ source libraries that extend the functional reach of the C++ Standard Library.

Boost acts as the primary incubator for the C++ Standard, with over 160 individual libraries covering linear algebra, multithreading, and image processing. Industry leaders like Adobe and Bloomberg rely on its high-performance components (such as Asio for networking and Filesystem for path manipulation) to build robust systems. The project maintains a rigorous peer-review process to ensure every library meets strict quality standards across multiple compilers and operating systems.

https://www.boost.org