One of the most noticeable differences between regular limes key limes is the size and color of the limes. More often than not, a key lime is smaller and more yellow than a regular lime. When sliced in half, you'll also notice that the key lime has a thinner skin and contains more seeds.
Key limes—also known as Mexican limes or West Indies limes—are small, spherical limes that grow in tropical and subtropical regions. They’re light yellow (not green) when ripe and contain more seeds than regular limes. Their skin is also very thin, which means they don’t store well. It’s best to keep them out of the fridge and use them within two days of purchasing.
Key lime juice is prized for being tart and super-aromatic. You can use them in place of regular limes in any recipe, but they’re an ideal choice for sweetened-up desserts like Key lime pie, cupcakes or thumbprint cookies.
These limes might get their name from the Florida Keys, but they’re grown all of over Florida and in some areas of California. They only grow in the U.S. between June and September, though. In Mexico, they enjoy a year-round season, but their delicate nature means transporting them to the U.S. can be challenging.