There is a carton in the back of your fridge with a date on it that came and went sometime last month, and you are standing at the open door doing math. Three weeks? Four? Does it count from when you bought them? The printed date is the least useful thing you are holding. Eggs are unusually honest about their own condition, and they tell you in about six ways: the shell, the smell, the color inside, how they sit in a glass of water, how the white behaves on a plate, and what they do in a hot pan. Learn those and the carton becomes a footnote.
The date on the carton is a suggestion
Three different dates can show up on an egg carton, and they mean three different things. A sell-by date is the last day the store should be selling them at peak freshness, which makes it a rule for the retailer more than for you. An expiration date marks the end of best quality, and on USDA-graded cartons it can fall no more than 30 days after packing. The pack date says when the eggs were washed, graded and boxed, and that one is the most useful of the bunch: the egg industry says eggs kept cold are generally good for four to five weeks past it.
That pack date is often hiding in plain sight as a three-digit number with no slashes in it, stamped near the plant code. It is a Julian date, counting days of the year, so 001 is January 1 and 365 is December 31. Once you know to look for it, you can tell how old a carton is before it ever leaves the store.
Cracks, including the ones you have to feel for
The shell is the whole defense system. Once it is broken, bacteria have a door and the egg loses the seal that keeps moisture in and air out. Obvious breaks are easy. The hairline ones are not, so run your fingertips over the shell instead of just looking at it. If one cracked on the way home, USDA’s advice is to break it into a covered container, refrigerate it and use it within two days.
There is a sneaky version of this that catches people. An egg that refuses to come out of the carton, or that leaves a little residue behind, may have a crack you never spotted: a bit of white can leak out and glue the shell to the cardboard. Sticking is worth a closer look. Check the ones on either side of it too.
A slimy shell ends the conversation
A fresh eggshell feels dry, matte and slightly chalky in a porous way. A shell that feels tacky or slick between your fingers has bacteria growing on it, and that slime is what they leave behind. It can be subtle, just a faint stickiness that makes you pause. Do not talk yourself out of it. The egg goes in the trash and your hands go under hot water, because whatever is on the shell is now on you.
Slime shows up faster when eggs live somewhere warm or damp. Keeping the fridge at 40 degrees Fahrenheit or below is the single biggest thing standing between your carton and that texture, and it is worth checking with a thermometer rather than trusting the dial.
Powder, fuzz and black spots
A dusty green film or a fuzzy black patch on a shell is mold, not dirt from the barn. The usual suspects on eggshells are Penicillium, Alternaria and Chaetomium, and they move in when eggs sit somewhere warm, humid or grubby on the way to you. Sometimes the first thing you see is not on the outside at all: dark spots on the inside of the shell when you crack it are the same problem, further along.
Wiping it off does not solve it. Mold sends out microscopic threads called hyphae that can push through the shell’s pores while the surface still looks like it only needs a rinse. An egg wearing mold is a lost egg, and the cure is storing the rest of the carton somewhere dry and cold so it does not happen again.
The float test measures age, not much else
Drop an egg into a tall glass of cold water. A fresh one sinks and lies flat on its side. An older one stands on end but stays under. A floater has a big enough air pocket inside to carry it up, which happens as moisture escapes through the shell and gas builds up in its place. Two details people get wrong: use cold water, and use plain tap water. Salt raises the density of the water, and enough of it will float even a brand-new egg.
A floating egg is old. It is not automatically a bad egg. The USDA’s position is that a floater may still be perfectly fine, and that the right move is to crack it into a bowl and check for odor or anything visibly off before deciding. Treat the glass of water as the screening round, not the ruling.
Your nose settles it
A fresh egg smells like nothing at all. A rotten one smells like sulfur, that struck-match, rotten stench you cannot mistake for anything else, and it comes from hydrogen sulfide gas forming as the proteins inside break down. There is no partial credit here. Faintly off still means out.
This is the argument for cracking every egg into a small separate bowl before it joins the batter or the pan. One bad egg dropped straight into six good ones costs you the whole bowl, plus whatever flour and butter went in with it. One caveat worth knowing: overcooked eggs also throw off a sulfur smell, and that is just chemistry, not spoilage.
Green, iridescent or pink inside the shell
Egg whites should be clear, maybe a touch cloudy. Whites with a green, pink or oil-slick iridescent sheen point to Pseudomonas bacteria, and a red tint points to Serratia. Same story on the yolk side: a greenish or strangely dark raw yolk is not a quirk of the hen’s diet. Eggs are supposed to look boring. Any creativity in the color is a reason to reach for the trash can.
Four things that look alarming and are not
People throw out a lot of perfectly good eggs. Blood spots, those little red specks on the yolk, come from a blood vessel bursting while the egg was forming, and the egg is fine. A cloudy white actually means the egg is very fresh, because carbon dioxide has not had time to escape through the shell yet. Those thick white ropes attached to the yolk are the chalazae, they hold the yolk in the center, and the more obvious they are, the fresher the egg.
The gray-green ring around a hard-boiled yolk is the other big false alarm. That is sulfur and iron reacting to heat because you boiled the egg too long, and it eats fine. Yolk color is not a freshness clue either. Hens fed wheat and barley lay paler yolks; hens on green plants, corn and alfalfa lay darker ones. And shell color tells you nothing at all, so a brown egg is not a better egg.
Watery whites, flat yolks and the shake test
Crack a fresh egg onto a plate and the white sits up in a tight mound around a domed yolk. Crack an old one and the white runs everywhere in a thin puddle while the yolk lies flat and breaks if you look at it wrong. That is age showing, and for scrambled eggs it barely matters, but for a fried egg or a poach it is the difference between a nice one and a mess.
Two quick tactile checks round it out. Hold an egg to your ear and shake it: if you hear liquid sloshing, the yolk has thinned out with age, which means old rather than automatically rotten. An egg that feels oddly light for its size has lost moisture through the shell, which is the same message arriving a different way. Crack either one into a bowl and let your nose make the call.
Foam in the pan
An egg that starts foaming and bubbling dramatically early in the cooking process, before the pan has really gotten to work, is venting gas produced by bacteria inside. A little sizzle and a few bubbles are normal. A cauldron impression is not. Slide it into the trash and start over with another egg.
Never use taste as a test. If a cooked egg smells or tastes off anyway, stop eating, scrape the plate, wash the pan.
The one sign that does not exist
Every check above catches spoilage. None of them catches Salmonella. The FDA is blunt about this: fresh eggs with clean, uncracked shells can still carry it, and a contaminated egg can look, smell and float exactly like a good one. That is why the agency tells shoppers to buy eggs only out of a refrigerated case, open the carton in the store to check for cracks, keep them at 40°F or below in their original carton, and use pasteurized shell eggs or pasteurized egg products in anything served raw or barely cooked, like Caesar dressing or homemade ice cream.
Worth knowing why American eggs live in the fridge at all: U.S. producers wash eggs before packing, and washing strips the cuticle, the natural coating that seals the shell. That leaves the shell porous. In much of Europe eggs are not washed, which is why they sit on a shelf in the store and yours cannot.
My actual rule
Slime, mold or a crack and the egg is gone on sight, no second opinion. Everything else gets the glass of water first, because it takes ten seconds and sorts the carton into use-now and use-soon. Then the egg goes into a small bowl on its own, and my nose makes the final decision, because a sulfur smell is the only signal that has never once been wrong.
The printed date stays at the bottom of that list. USDA advises using refrigerated shell eggs within three to five weeks, and tossing a whole dozen because a stamp on the cardboard rolled over is just money in the garbage. Keep them in the carton, keep them cold, keep them off the door where the temperature swings every time someone grabs a soda, and let the eggs tell you when they are done.
