Recording first and going live later is normal broadcasting. Television has done it for seventy years. On the streaming platforms it takes a little care, because the tools assume a camera and a person, and the rules differ from one platform to the next.
A one-off. You have a finished video and want it to go out live at a set time, with chat, then end. YouTube calls this a Premiere and has a built-in tool for it that needs nothing else. Twitch and Facebook have no equivalent, so the video has to be sent to them as a live stream by something.
An always-on channel. The video, or a playlist, plays continuously and the broadcast never ends. No platform has a built-in tool for this. It needs something sending the video around the clock, which is what the rest of this page covers.
YouTube allows pre-recorded content live, with no broadcast limit. Reused content is judged under the same policies as uploads, so a channel that only replays other people's video will not get far; your own back catalogue is fine.
Twitch allows it, ends every broadcast at 48 hours, and its rules on reruns are its own. A rerun channel should say it is one.
Facebook and Instagram end a broadcast at 8 hours and hand out a key that only works for that one broadcast unless you ask for a persistent one.
Kick, Rumble and anything with an RTMP address take a stream like any other. Beamd can send to any of them at once from one source.
Viewers do not mind a replay. They mind being told it is live when it is not. A title or description that says replay, rerun or 24/7 keeps you on the right side of every platform's rules and of your audience.
One stream can go to several destinations at once, and a destination that wants a vertical picture, such as a YouTube dual stream key, gets one cut from the same video. Each destination counts against your plan's allowance; the video is sent once.
Stream 24/7 with your computer off