The difference between "in" & "im" is easy to understand. The word "im" in German is short for "in dem". The word "in" means "in" or "into" in English. So, just like in English, you'd say "I am in the café", but "I am in London".
At first glance, it can appear as though the words in & im are interchangeable, but this is not the case. While they may sound similar, they actually have very different meanings, and they cannot be used interchangeably.
What's the Difference between in & im in German?
Meaning of in
Let's start with in: In is a two-letter preposition that is used to indicate location or direction. It can be used to describe a place, or to indicate a direction of movement. For example:
Or you could say:
What's important is that in describes movement or direction and that what comes after can have an article (in den Park) or also not (Ich bin in London).
Meaning of im
Now let's turn to im: Im is a three-letter preposition, and it is as short for in dem. For example:
Here, you can use im, but you don't strictly have to. You could also just say in dem Internet - although that doesn't sound so natural.
So, in conclusion, in some cases you can use im (and you should, because it sounds better), and in other cases you can't (when, for example, the object doesn't have an article, e.g. in London, since im is only a replacement for in dem).