Definition
This idiom expresses the idea that one will only believe something if they have seen it themselves, especially if the thing is unusual or unexpected.
I never believed in ghosts until I saw one myself; seeing is believing.
She claimed she could levitate a pencil. I didn’t believe it, but seeing is believing. She actually did it.
I had heard that the food at this restaurant was delicious, but seeing is believing; I only truly believed it after tasting it myself.