Streaming and subscriptions

The sentence this list is built to warn you about is Das Abo verlängert sich automatisch. Look at the sich. English lets a subscription renew, a price rise and a deadline move all on their own: the verb just loses its object and carries on. German does not let verlängern do that. When the contract itself is what gets longer, and nobody is doing the lengthening, the empty object slot is filled with the reflexive, and the subject lengthens itself: der Vertrag verlängert sich, der Preis erhöht sich, die Frist verschiebt sich. Leave the pronoun out and the sentence sounds unfinished, as if the contract were about to extend something else. Read the other way round, the little word is a useful alarm. Wherever a German contract says verlängert sich, nobody has to lift a finger for it to happen — which is exactly why you have to.