How long does opened yogurt last in the fridge?

Short answer: an opened tub of yogurt, kept properly cold, is usually fine for one to two weeks — often closer to two if it is a plain, spoon-clean tub kept toward the back of the fridge rather than the door. That is a wider window than most people assume, and the reason comes down to what yogurt actually is: a food that is already fermented and full of live bacteria before you ever break the seal, which makes the printed date a more conservative number than the one on, say, a carton of milk.

Why the printed date is a strange starting point for yogurt

Milk spoils because bacteria move in and start multiplying. Yogurt is milk that bacteria have already been through, on purpose, under controlled conditions, to turn it into something more acidic and more hostile to the bacteria that cause ordinary spoilage. That is the entire reason yogurt exists as a food category — the fermentation is a preservation step as much as a flavour one. The date on the lid is still a real estimate of quality, mostly texture and tartness drifting over time inside a sealed, unopened tub, but it is not measuring the same kind of vulnerability a printed milk date is measuring. Opening the tub does not switch on spoilage the way opening a carton of milk does; it just starts exposing an already fairly defended food to the outside world a little at a time.

What actually determines how long it keeps

Temperature, as always. Yogurt kept at a genuinely cold, steady temperature holds its two-week-ish window; yogurt that spends time in the door, where the temperature swings every time someone opens the fridge, does not. Moving it to the main body of the fridge is the single easiest thing that extends how long it stays good.

What touches the spoon. A spoon that has been in a mouth and goes back into the tub carries bacteria into an environment that is otherwise mostly working in your favour. This is the biggest single reason a home-opened tub does not last as long as an unopened one on the shelf — not time, but repeated small contamination from the way it gets eaten. Scooping out a portion into a bowl rather than eating straight from the tub is a small habit that noticeably extends the tub's life, for exactly this reason.

How well it is resealed. A lid pressed back on loosely, or a tub left slightly open in the fridge, dries out the surface and lets in more of the air and airborne mould spores that eventually do become the real problem. A tight seal matters more for yogurt than people expect, given how defended the product already is against ordinary bacterial spoilage.

The liquid on top is not a warning sign

A thin layer of watery liquid sitting on an opened tub, especially after a few days, is whey — a natural byproduct of the fermentation, separating out as the proteins in the yogurt settle. It is not a sign the tub has gone off, and it is not the same thing as the liquid pooling under a spoiled food. Stir it back in, or pour it off if the texture bothers you; either is fine, and neither one is a food-safety decision. This is one of the more common reasons a perfectly good tub gets thrown out — the liquid looks like something has gone wrong, when it is actually just yogurt being yogurt.

Signs it has actually turned

Because yogurt is already sour and already textured in a way that reads as "a bit off" to someone unfamiliar with it, the useful signs are the ones that go beyond its normal character rather than the ones that sound alarming out of context. Mould — any fuzzy or coloured spot on the surface, not just a general tang — is the clearest signal, and if you see it, the safe move is to treat the tub as done rather than scrape around it, since mould in a soft, wet food can spread further than what is visible on top. A smell that has gone from tangy to genuinely unpleasant, or a texture that has separated into something closer to lumps and liquid than a uniform tub, are the other two worth trusting over the calendar. None of this is a rule you need to memorise in advance — it is closer to noticing that something smells or looks different from every other spoonful you have had from that tub, which is a comparison most people are already equipped to make.

Greek, plant-based, and the rest

The general shape holds across types, with small shifts. Greek yogurt, being lower in moisture after straining, tends to hold up at least as long as regular yogurt and sometimes a little longer. Plant-based yogurts vary more by brand and base ingredient than dairy ones do, so the tub's own guidance after opening is worth trusting over a general rule here. Flavoured yogurts with fruit or syrup mixed in tend to turn a little sooner than plain, since the added sugar and moisture give any stray bacteria more to work with.

This is close to what Munch's opened-item tracking is actually for. Marking a tub as opened starts its own countdown from that day rather than from the date printed on the lid, visible to everyone in the household, so the yogurt at the back of the shelf is not relying on someone's memory of when it was first opened three weeks ago.

None of this needs to be treated as a special case. It is the same fact that shows up everywhere in a fridge: the date on the package describes an unopened product, and once it is opened, what actually decides how long it lasts is temperature, cleanliness, and how well it is sealed back up — yogurt just starts that clock from a more forgiving place than most.