Short answer: a floated egg usually means it’s older and has a larger air cell; it may still be safe to eat, but freshness and safety aren’t guaranteed, so don’t rely on it alone. Details

• Freshness test: the classic “float test” works because eggs lose moisture and air enters through the shell over time, enlarging the internal air pocket. A fresh egg tends to sink; an older egg may tilt or float due to that larger air cell.

• Safety caveats: a floating egg is often older and more likely to be spoiled, but floating does not definitively indicate rottenness. If an egg floats, inspect it further: smell, look, and consider how long it’s been stored. If in doubt, discard.

• Practical guidance: use the float test as an initial check, then crack the egg into a separate bowl to assess smell and appearance before cooking. If there’s any bad odor or unusual color, discard.

What to do if it floats

• Do not rely solely on the float test to determine safety. Break the egg into a clean dish and assess: odor is the strongest warning sign; a rotten egg often has a sulfurous or foul scent after cracking. If no odor and the texture looks normal, it may still be safe to use, but proceed with cooking and use within normal timeframes.

When to discard immediately

• If the egg has an obvious off smell after cracking, or if there are unusual colors in the yolk or whites, discard.

Bottom line

• Floating typically indicates an older egg with a larger air cell; it might still be safe but should be checked carefully rather than assumed rotten. If in doubt, err on the side of caution and discard.