OBS Studio 29.1.3: OBS is free, open source video recording and editing software. It is open source and cross platform (Windows, Mac, Linux). It can record video, and make streaming of everything happening on your computer screen.
It is written in C and C++, and uses all known and unknown streaming services of our time: Twitch.tv, Youtube/Youtube Gaming, hitbox, beam.pro, Daily Motion, Livecoding.tv, Web.Tv, and many others still.
Of course, it can also be used to record on video what is happening on your computer screen, even if you are playing a game.
It takes advantage of DirectX 11 but you can also configure it for OpenGL. For video encoding, it uses, among others, codec features such as x264 free software library, Intel Quick Sync Video and Nvidia NVENC to create video streams in H.264/MPEG-4 AVC format, offering the best possible ratio between the file size and the quality.
GitHub releasenotes
Download the application on the platform you are interested in