Answer: Milk is not keto-friendly, but plenty of keto-friendly alternatives exist.
Milk is unfortunately not compatible with the keto diet.
Among the different options for milk, whole milk and raw milk are the most closest to keto-friendly as they have the highest amount of fat. The macros vary a bit between whole, 2%, 1%, and skim, but they each contain ~12 g of net carbs per cup, which is very high. Full-fat, whole milk is the closest to being keto, as it does contain high fat content despite its high carbs.
Fortunately, coconut milk and almond milk are keto-friendly replacements that you can often swap in for recipes that call for milk. Macadamia milk is a growing trend, and it's keto-friendly as well. Stick to unsweetened, unflavored milks, and always check the label, but it should be easy to find almond milk or coconut milk with 1 g or less of net carbs.