Cold open

Television got there first: a scene runs before the titles so you are hooked before the theme tune starts. On YouTube a cold open means dropping the branded intro and the hello-everyone-welcome-back entirely and opening on the most interesting moment you have. Sometimes that is the payoff shot from the end. Sometimes it is a line of dialogue mid-argument. The reason it took over is that generic preamble spends the first 10 seconds, when viewers are still deciding whether to keep watching, on something nobody clicked for.