The phrases and what they mean
- Best if used by / best by — the manufacturer’s estimate of peak quality. Not a safety date.
- Sell by — stock-rotation information for the retailer. The food is normally fine for days or weeks after, if stored properly.
- Use by — the last date of peak quality as judged by the manufacturer. In the US this is still generally a quality date — unlike the EU/UK, where “use by” is a legal safety limit.
- Freeze by — freeze on or before this date to preserve peak quality.
The exception: infant formula
Infant formula is the one product with a federally regulated use-by date, tied to nutrient content and quality. Never use formula past this date, and follow the package preparation instructions exactly — see the infant formula page.
So what actually governs safety in the US?
Storage time and temperature, not the printed date. A carton of milk “good until” next week becomes hazardous in an afternoon on a hot counter; cooked chicken is a 3–4 day food once refrigerated regardless of any date on the original packaging. That is why the tools on this site ask when you bought, opened, or cooked something — the printed date alone cannot answer a safety question.
Common mistakes
- Discarding perfectly good food the morning of its sell-by date.
- Keeping opened deli meat two weeks because the unopened-package date says so.
- Applying US date-label logic to EU/UK products or vice versa.