You may have noticed some eggs float in fresh water, while others don’t and have wondered what this means for egg quality. While it’s been said that means the eggs have gone bad and should be thrown out, a floating egg does not necessarily equal a bad egg.
Eggs have an air cell that becomes larger as the egg ages and acts as a buoyancy aid. An egg can float in water when its air cell has enlarged sufficiently to keep it buoyant. This means the egg is older, but it may be perfectly safe to use.
To determine if your egg is buoyant, but still usable, crack the egg into a bowl and examine it for an off-odor or unusual appearance before deciding to use or discard it. A spoiled egg will have an unpleasant odor when you break open the shell, either when raw or cooked.