OBS Studio (from Open Broadcaster Software) is a free, open-source desktop application for video recording and live streaming. It runs on Windows, macOS and Linux. Lain created it and maintains it, and the OBS Studio contributors develop it.
A user builds scenes from sources: window captures, images, text, browser windows, webcams, capture cards and more. OBS captures and mixes the video and audio in real time, with per-source audio filters such as noise suppression, and switches between scenes through transitions and hotkeys. Studio Mode shows a preview of a scene before it goes live. OBS encodes the result, for example as H.264 video with AAC audio, and either sends it to Twitch, YouTube and other streaming services or saves it as a recording. An API lets native plugins and scripts in Lua or Python add functions.
OBS Studio is free. The source code is under the GNU General Public License v2 or later, and the project is funded by sponsors and backers.