You can and should deep fry your french fries while they are still frozen. This will reduce cooking time and enhance your fries’ quality, as deep frying them will make them deliciously crispy on the outside and soft on the inside.
While they typically will be somewhat less tasty and crispy, you can certainly still eat McDonald’s fries the next day. They can be kept in the fridge for 1 to 2 days and then reheated in a microwave or an air fryer.
While most french fries have a shelf life of 12 to 18 months in the freezer, they may already lose some of their quality and taste after 6 months. If stored appropriately, they generally last 3 to 5 days in the fridge.