How long does a cut avocado last in the fridge?

The short version: half an avocado, pressed tight against something to keep air off the cut surface and refrigerated, is usually fine to eat for about a day, sometimes stretching to two. What limits it is not really the calendar, and it is not bacteria doing the same thing that turns milk sour. It is oxygen reacting with the flesh the moment you expose it — a completely different mechanism from the one this site usually talks about, and one that means a browning avocado is not automatically a spoiled one.

Why the cut surface is the whole story

Avocado flesh contains an enzyme, polyphenol oxidase, that sits inertly inside the cells until a knife breaks them open and lets it meet the air. Once that happens, the enzyme starts oxidising compounds in the flesh, and the visible result is that familiar brown-grey rind spreading in from the cut edge. This is the same basic chemistry as a sliced apple browning, and it has nothing to do with the ripeness clock that governed the avocado before you cut it. A rock-hard avocado you cut open too early will still brown on the cut face; a perfectly ripe one will too. Cutting it is what starts this particular clock, not how ripe it was.

What actually slows it down

Because the reaction needs oxygen, almost everything that helps here is really one idea wearing different outfits: keep air off the exposed flesh. Pressing plastic wrap directly onto the cut surface, rather than loosely over the container, matters more than the container itself. A splash of lemon or lime juice brushed over the flesh works for a genuinely different reason — the acid slows the enzyme down directly, not just by blocking air — which is why it noticeably outperforms wrap alone. Submerging the cut side down in a shallow layer of water in a sealed container is another way of doing the same job, and it holds off browning surprisingly well for a day or two. Leaving the pit in only protects the small patch of flesh actually touching it; it is not doing anything for the rest of the surface, whatever the kitchen folklore says.

Browning is not the same question as spoiled

This is the distinction worth actually remembering. A thin brown-grey layer on the surface is oxidation, not decay, and scraping it off a piece that is otherwise green and creamy underneath, with a normal smell, is a reasonable and widely used move — you are removing the part that reacted with air, not treating the fruit as compromised. What signals the avocado has actually gone, rather than just browned, is different and more obvious once you know to look for it: flesh that has turned uniformly dark brown or black all the way through rather than just at the surface, a texture that has gone slimy or stringy rather than soft, or a smell that reads as off rather than simply neutral. As with any food, when it clearly crosses into that territory, the safer move is to treat it as done rather than try to rescue it.

Freezing works, but only if you change its form first

A whole or halved avocado does not come back from the freezer well — the texture that made it worth eating in the first place turns watery and grainy once thawed, because ice crystals rupture the same cell walls that gave it that texture to begin with. Mashed avocado, with a little lime juice mixed through to slow browning further, freezes considerably better, because you have already accepted the texture change before it goes in. If a batch is destined for guacamole or a spread rather than being sliced onto something, mashing it before freezing is the move that actually works, rather than hoping a whole one will thaw back into itself.

The part that is easy to lose track of

An avocado is an unusually all-or-nothing item in most kitchens — a whole one gets bought, half gets used, and the other half goes back in the fridge wrapped in whatever was on hand, with no obvious marker of when that happened. A day later it looks basically the same from the outside as it did an hour after cutting, which makes "is this the one from yesterday or the one from Tuesday" a genuinely hard question to answer just by looking.

This is close to what Munch's opened-item tracking is for more generally: marking something as opened starts its own countdown from that day, separate from whatever date applied before you cut into it, visible to everyone in the household rather than only to whoever reached for the knife first — so the half avocado at the back of the shelf is not relying on a guess about which day it was cut.

None of this needs remembering a rule about avocados specifically. It needs one habit that works on almost anything cut open in a kitchen: keep air off the exposed part, and know roughly when it happened.