Closing an old card can feel like simplifying your finances, but it can also work against your credit score in two specific ways: it reduces your total available credit, which raises your utilization percentage, and it can eventually shorten your average account age.
If the card has no annual fee, many people choose to keep it open and use it occasionally to prevent the issuer from closing it for inactivity. If it does have a fee and you rarely use it, the calculation becomes more personal and depends on your broader credit picture.
There is no universally correct answer here, it depends on your full credit profile and goals. This article is general education, not a recommendation for your specific situation.