What apps do people use to buy and sell second-hand items in Korea?

The most popular one by far is Danggeun Market (당근마켓, Karrot), a hyper-local app where you buy and sell used items with neighbors and meet nearby to hand things over. Bunjang (번개장터) and Joonggonara (중고나라) are also widely used, especially for electronics and a wider selection. To stay safe as a foreigner, prefer in-person direct deals (직거래) in public spots for local items, check the seller's rating on Danggeun, and for anything shipped or pricey, use the in-app safe-payment escrow (안전결제) rather than sending money directly to a stranger's account, which is the main way scams happen. A translation app helps with listings, but Danggeun's interface is simple enough that most foreigners pick it up quickly.