Can I wear these with socks, or are they designed to be worn barefoot?

Either — they're built to work both ways.

Barefoot is where you'll notice the footbed most: it has a soft, suede-like top layer and subtle toe ridges that your toes press into as you walk. With socks that texture is less pronounced, but nothing about the fit or support changes — the Flyknit upper stretches to accommodate either.

Most people end up doing both: barefoot around the house in warmer months, thick socks in winter.

One sizing note: if you're between sizes and plan to wear them with thicker socks, size up.