obsproject/obs-studio

OBS Studio (Open Broadcaster Software) is a free, open-source application for recording your screen and streaming live video to platforms like Twitch, YouTube, or Facebook Live. It solves the problem of capturing and mixing multiple video and audio sources (game capture, webcam, microphone, browser windows, etc.) into a single composed output stream or recording. It is the go-to tool for streamers, content creators, educators recording tutorials, and developers doing demo recordings. The software works by letting you set up multiple scenes, where each scene can contain different sources arranged as layers: a game capture layer, an overlay image, a webcam feed, a chat box, and so on. You switch between scenes during a stream to change what viewers see. The captured content is encoded using hardware or software encoders (supporting formats like H.264, HEVC, and AV1) and then either saved as a local file or sent to a streaming service over the RTMP or SRT protocols. Under the hood it uses FFmpeg for encoding and DirectShow on Windows for device capture. It supports a plugin system, which is why a large ecosystem of third-party extensions exists. You would use OBS Studio whenever you need to stream or record video content on your computer. It works on Windows, macOS, and Linux. The core application is written in C and C++, making it efficient and capable of handling high-resolution, high-frame-rate capture without taxing lower-end hardware too much. It is distributed under the GNU General Public License v2 and has no cost or subscription requirement.