How To Test If An Egg Is Good Or Bad? Expert Tips

The most reliable test for a bad egg is your nose. A spoiled egg produces hydrogen sulfide and other compounds that give off a distinct sulfur or rotting smell the moment you crack it. If the egg smells fine, the next check is the float test: a fresh egg sinks in water, an older egg stands upright, and a truly bad egg floats. Those two checks — smell first, float second — will catch almost every egg you should not eat.

Eggs are one of the few foods with a built-in freshness indicator: the shell, the air cell inside it, and the way the contents behave when you crack them open. Learning to read those signs takes about a minute and can save you from a stomach bug or a wasted breakfast.

How To Test If An Egg Is Good Or Bad Using the Float Test

The float test works because of a simple physical process. Eggshells are porous. As an egg ages, moisture escapes through the shell and air seeps in to replace it. That air collects in a pocket at the wide end of the egg called the air cell.

The older the egg, the bigger the air cell. A fresh egg has almost no air inside, so it sinks and lies flat on the bottom of a bowl of water. An egg that is a few weeks old has enough air to make it stand upright on one end. An egg with a large air cell floats.

Here is how the results break down:

• Sinks and lies flat: very fresh, ideal for poaching or frying
• Sinks but stands upright: older but usually still safe to eat, best for hard-boiling or baking
• Floats to the surface: old enough that the air cell is large; this is a warning sign, not proof of spoilage

That last point matters. A floating egg is not automatically rotten. Floating tells you the egg is old. Smell and appearance tell you whether it is actually spoiled. Many people treat “floats” as a hard fail, but the float test is a freshness gauge, not a safety test on its own.

What Does the Smell Test Tell You?

Smell is the single most dependable sign of a spoiled egg. Crack the egg into a separate bowl — never directly into your pan or batter — and smell it before adding anything else. A good egg has little to no odor, or a faintly neutral one.

A spoiled egg releases a sulfur-like, rotting smell. That odor comes from bacteria breaking down proteins and producing hydrogen sulfide and related compounds. If you catch that smell, throw the egg out and wash the bowl and your hands before continuing.

Cracking into a separate bowl is not just about smell. It keeps a bad egg from contaminating an entire batch of cookie dough or an omelet. It also lets you fish out stray shell fragments before they end up in the food.

How Can You Tell If an Egg Is Bad After Cracking It?

Once the egg is in the bowl, look at it. Three things are worth checking.

The yolk. A fresh yolk is round and sits up firmly. As an egg ages, the yolk membrane weakens and the yolk flattens. A flat yolk is a sign of age, not necessarily spoilage.

The white. Fresh egg whites are thick and stay close to the yolk. Older whites get thin and runny and spread out across the bowl. Again, this reflects age more than safety.

Color and texture. A spoiled egg may show discoloration — pink, greenish, or iridescent tints — or a cloudy, unusually watery appearance. Discard any egg with discolored whites or a yolk that has broken and looks off.

One thing people often mistake for spoilage: a cloudy egg white. Cloudiness actually indicates a very fresh egg. It comes from carbon dioxide that has not yet escaped through the shell. Cloudy whites are a good sign, not a bad one.

Can You Trust the Egg Carton Date?

Carton dates are useful but they are not the same as a safety deadline. In the United States, the “sell-by” or “expiration” date on an egg carton is set by the producer or state rules, not by a single federal standard. The USDA grades eggs for quality, and the date reflects the producer’s estimate of peak quality rather than a hard cutoff for safety.

Refrigerated eggs generally keep well for several weeks past the date on the carton, though quality — flavor, texture, how well the white holds together — declines over time. The date is a quality guide. Your nose and eyes are the safety check.

One important exception: how the eggs were stored matters more than the date. Eggs left at room temperature age far faster than refrigerated ones. In the US, eggs are washed before sale, which removes a protective coating on the shell. That is why US eggs are refrigerated. In many other countries, eggs are not washed and are often stored at room temperature. The storage advice that comes with your eggs reflects how they were handled, so follow the carton’s guidance.

What About the “Bad Egg” Signs You Should Never Ignore?

Some signs are clear and should end the discussion. Throw the egg away if it has any of these:

• A sulfur or rotting smell when cracked
• Discolored white or yolk — pink, green, or rainbow sheen
• A shell that is cracked, leaking, or covered in a powdery or slimy film
• Mold visible on the shell or under it

A cracked egg is a specific concern because bacteria can enter through the break. A clean crack found at home, cooked thoroughly and eaten right away, is usually fine. A cracked egg that has been sitting in the fridge for days, or one with visible leakage, is not worth the risk.

Salmonella is the main foodborne concern with eggs. The CDC estimates that Salmonella causes a substantial number of foodborne illnesses in the US each year, and eggs are one recognized source. Thorough cooking — until both yolk and white are firm — kills Salmonella. This is why raw or undercooked eggs are a particular concern for young children, older adults, pregnant women, and anyone with a weakened immune system.

Does a Fresh Egg Always Mean a Safe Egg?

No, and this is where a lot of home testing advice goes wrong. Freshness and safety are related but not identical. An egg can be fresh and still carry Salmonella on or inside the shell. An egg can be old and completely safe to eat if it was handled and stored properly.

That is why the float test and the smell test are best used together as a freshness and spoilage check, not as a guarantee of safety. The only reliable way to eliminate the Salmonella risk in an egg is to cook it thoroughly. For recipes that call for raw or lightly cooked eggs, pasteurized eggs are an option that carries a much lower risk.

There is no home test that confirms an egg is free of bacteria. If you want certainty on safety, cooking is the answer, not testing.

How Should You Store Eggs to Keep Them Good Longer?

Proper storage slows the aging process and keeps eggs safe. Keep eggs refrigerated at a consistent temperature — food safety guidance places safe refrigeration at 40°F or below. Leave them in their original carton rather than the door, where temperature fluctuates each time the fridge opens.

Store eggs with the wide end up. The air cell sits at the wide end, and keeping it up helps the yolk stay centered and reduces the chance of the air cell pressing on the yolk.

Do not wash eggs before storing them. Commercial eggs in the US are already washed, and rewashing at home can push bacteria through the shell or remove protective layers. If an egg is visibly dirty, it is safer to discard it than to wash and store it.

Hard-boiled eggs are a separate case. Cooking removes the shell’s natural defenses, so hard-boiled eggs should be refrigerated and eaten within about a week. That is a standard food safety guideline, not a freshness estimate.