A dark pattern is a UI technique designed to trick users into doing things they didn't intend to. For example, hiding the Delete account button to keep users registered or sneaking extra items into users' shopping carts.

Dark patterns aren't examples of accidental bad design. They are created with a solid understanding of human psychology to deliberately deceive users. Dark patterns don't carry users' interests in mind and conflict with the principles of human-oriented design. In the long run, dark patterns are not good for the business's reputation.