I get curious about this every time I cut open a lime: How can these citrus fruits not have seeds? Or are they just so tiny, I can't see them? Turns out, the limes typically sold in supermarkets, Persian or Tahiti limes, are indeed seedless. Petite key limes, on the other hand, contain seeds.
Seedless limes are classified as a parthenocarpic fruit, meaning their flowers don't require pollenating to make fruit, which results in zero seeds. Though some fruits are bred to have no seeds, seedless limes are naturally occurring, so squeeze away.