In most cases, brown bananas are safe to eat. Bananas are picked green, then as the fruit ripens, the peel changes from green to yellow, and then to yellow with a few brown speckles. If you don't eat the banana, it gradually turns dark brown and becomes softer and sweeter, though it will eventually go bad.
Let Your Senses Be the Boss
Your senses will tell you if the banana is rotten. Don't eat a banana it if smells bad, if it's extremely squishy or leaking liquid, or if you notice mold, especially around the stem. If in doubt, always throw it out. To keep ripe bananas from turning brown, store them in the refrigerator. Although the peels will turn dark brown, the inside of the bananas remains fresh and flavorful for several days. If the bananas are too ripe for your liking, use them in smoothies or banana bread.