"I don't believe you" or "I don't believe it"?
When someone say something and I don't believe, should I use "I don't believe you" or "I don't believe it"?

I think I can use both but do I understand correctly?

I don't believe you = to emphasize the person I talk to.
I don't believe it = to emphasize the thing the person talks about

Question

"I don't believe you" or "I don't believe it"?
When someone say something and I don't believe, should I use "I don't believe you" or "I don't believe it"?

I think I can use both but do I understand correctly?

I don't believe you = to emphasize the person I talk to.
I don't believe it = to emphasize the thing the person talks about

Answer

Yes, exactly. You can also use 'I don't believe it' when talking with another person or persons about something none of you is sure about, e.g. something that might happen that no-one is sure is true - e.g. 'they say the boss is going to resign next week, I don't know if it's true' - 'I don't believe it!'.