$US USDD (Decentralized USD) is a decentralized, over-collateralized stablecoin designed to maintain a 1:1 peg with the US dollar and can be used in multi-chain and DeFi ecosystems. Mechanically, USDD is not fully backed by fiat reserves, but relies on various crypto assets as over-collateralization, combined with market adjustment mechanisms to maintain price stability. This design theoretically enhances capital efficiency.