StockX: a popular marketplace for buying and selling authentic sneakers, streetwear, and other items.
GOAT: a similar platform to StockX, that specializes in authenticating and reselling shoes.
eBay: a general e-commerce platform where you can sell kicks and other items.
Grailed: a marketplace for high-end men's fashion.
Depop: a social shopping app where you can sell various items to a community of buyers.