Have a specific camera model that uses index.shtml? Check the comments or your manufacturer's developer docs for the direct stream URL syntax.

While most modern cameras use RTSP or MJPEG over simple .html or .php files, the .shtml extension signals a different beast. It indicates that the server is using Server Side Includes (SSI).

Do not view the camera through the SHTML page. Extract the underlying MJPEG or JPEG stream and inject it into a modern video player (VLC), a surveillance suite (Blue Iris), or a home automation dashboard (Home Assistant).