This page is about Duolingo’s explanation on how German dative prepositions work. I need to keep this explanation close since it’s difficult to remember the prepositions.

Dative prepositions

aus, aüßer, bei, gegenüber, mit, nach, seit, von, zu

Accusative prepositions

bis, durch, für, gegen, ohne, um

2-way prepositions

Two-way prepositions take the date case or the accusative case depending on the context.

If there is movement or if there’s movement within a certain place, use the dative case

an, auf, entlang, hinter, in, neben, über, unter, vor, zwischen

No movement -> dative:

Ich bin in einem Haus

Movement within a certain place -> dative:

Ich laufe in einem Wald

Movement from one place to another -> accusative:

Ich gehe in ein Haus

Contractions

Some prepositions and articles can be contracted.