I've had some married friends who met online, and I'm honestly not sure what the recipe for success is from observing them as well as the ones that failed.

I guess a sense of realism, because online relationships can tend to get melodramatic and prone to like...fantasies or w/e. So there needs to be a real tangible course of action for meeting up irl and cementing it. Otherwise, it's just a placeholder until one partner finds someone irl or gets tired of the situation.