Is there any difference between "just to let you know" and "just let you know"?
Is there any difference between "just to let you know" and "just let you know"?
Do they all mean "In addition""I just want you to know"?

And I don't understand they are used in what kind of situation.

Question

Is there any difference between "just to let you know" and "just let you know"?
Is there any difference between "just to let you know" and "just let you know"?
Do they all mean "In addition""I just want you to know"?

And I don't understand they are used in what kind of situation.

Answer

As a sentence modifier like "by the way" or "for your information", it should be "just to let you know". The second example can't be used that way, but it might be in a sentence such as "Tell Bob to just let you know when he has finished".