Window Capture Limitations

1. Only available for Microsoft Windows (gdigrab). Linux (x11grab) and macOS (avfoundation) capture devices do not provide this feature. However, there is a workaround documented in the wiki.
2. Always stop the recording before closing the application. Otherwise, ffmpeg will force exit as soon as the window disappears and may produce an invalid video file.
3. If you're launching multiple applications or testing an application at different window sizes, recording the desktop is a better option.
4. #fetch only returns the title from a currently active (visible) window for the given process.
5. #fetch may return ArgumentError (invalid byte sequence in UTF-8) for a window title with non UTF-8 characters. See wiki for workaround.
6. Disable Hardware Acceleration to avoid capturing a black video. See wiki entry for this here.