The shelf life of plain unsweetened yogurt in the fridge can vary depending on various factors, such as the brand, the packaging, and the specific ingredients used. Generally, plain unsweetened yogurt will last anywhere from 1 to 2 weeks in the refrigerator if it remains unopened and properly stored.
Once you open the container, the yogurt's lifespan will decrease. In most cases, you can expect it to stay good for about 5 to 7 days after opening, provided it is stored in an airtight container.
Keep in mind that these timeframes are approximate and that the actual freshness of the yogurt may vary. Always check the expiration date on the package and use your senses (look, smell, taste) to determine if it's still safe to eat, especially if it's been in the fridge for a while. If you notice any signs of spoilage, such as an off smell, mold, or an unusual texture, it's best to discard it.