Measurement Kit is a C++14 library that implements open network measurement methodologies (performance, censorship, etc.) on Unix-like operating systems such as Android, iOS, Linux, and macOS. It is meant to be embedded by third party applications with specific network measurement needs and/or to be used by researchers to implement novel network measurement tools. It started as a common engine to implement the mobile versions of OONI and Neubot, and since then has grown to include also the implementation of Portolan traceroute and NDT tests.