Fridge door not sealing properly

A fridge door that doesn't seal properly (you can see light around the edge, or it doesn't hold the magnetic seal) lets warm air in constantly and makes the whole unit work harder than it should. Check the gasket for cracking or flattening — it's a wear item over years of use and a straightforward DIY replacement on most units. If the gasket looks fine but the door still doesn't seal, the door itself may be slightly warped or misaligned on the hinges. Does the gasket look intact, or visibly worn/flat?