Perishable food left at room temperature for more than 2 hours goes in the trash. Above 90°F, the limit is 1 hour.
Most cooked leftovers keep 3–4 days in a fridge at 40°F or below. Freeze anything you won't finish in time.
Do not taste food to check it. If it smells off, shows mold, or sat out too long — discard it.
Almost every date printed on American food packaging is about quality, not safety. With one exception, federal law does not require them and does not define what they mean — manufacturers set them themselves.
"Sell by" is an instruction to the store telling staff when to pull stock from the shelf. You are expected to keep the food at home afterwards. "Best if used by" is the manufacturer's estimate of peak flavor and texture. "Use by" is the last date for peak quality — and it is a genuine safety deadline for exactly one product, infant formula, which is the only food with a federally regulated date.
So a carton of milk three days past its sell-by date that has been kept properly cold is usually fine, and a package of chicken bought fresh today but left in a warm car is not. How the food was handled matters more than what is stamped on it — which is why every page here gives you a window measured from when you brought it home.
The danger zone is 40°F to 140°F. Bacteria multiply fastest in that range, which is why the two-hour limit exists: perishable food held there for more than two hours has had enough time for meaningful growth, and reheating does not reverse it. Some bacteria produce heat-stable toxins that survive cooking entirely, so food left out too long cannot be rescued by cooking it harder.
The second rule is that refrigerator windows are about safety and freezer windows are about quality. Food held at 0°F stays safe indefinitely; the months we list for the freezer are the point past which texture and flavor noticeably decline. Past a refrigerator window, discard it — regardless of how it looks or smells.
That last point is the one worth internalizing. The bacteria that make food smell bad are largely not the ones that make you ill, so your nose is not a safety test. When a food is past its window, the USDA's advice is the same one we end on: when in doubt, throw it out.
More on where these numbers come from in our editorial policy, or read about the site.