Boost provides free peer-reviewed portable C++ source libraries.

We emphasize libraries that work well with the C++ Standard Library. Boost libraries are intended to be widely useful, and usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use.

We aim to establish existing practice and provide reference implementations so that Boost libraries are suitable for eventual standardization. Many Boost libraries are included in the C++ Standards Committee's Library Technical Report (TR1), in the C++11, C++14 and C++17 standard. More Boost libraries are proposed for standardization in C++20.

Since 2006 an intimate week long annual conference related to Boost called C++ Now has been held in Aspen, Colorado each May. Boost has been a participant in the annual Google Summer of Code since 2007.