Take-out pizza from locations like Pizza Hut and Dominoes can be left out unrefrigerated for up to 24 hours. Pizza tends to become dry and hard when it sits at room temperature for too long.
Frozen pizza that has been cooked should not be left out for more than a few hours, and homemade pizza follows the same rule. If properly stored, these types of pizza can be safely kept inside the refrigerator for 3 to 5 days.
If pizza has a foul or rancid smell or shows signs of mold, it poses a threat of food-borne illness and should not be consumed.