There are many ways to trade the dollar index. The easiest way for stock traders to trade DXY is through ETFs. UUP, for example, is an ETF that provides bullish exposure to the dollar index. When DXY goes up, UUP goes up, and vice versa. UDN is essentially the opposite—an ETF that provides bearish exposure. Futures traders can trade DXY through USDX. Forex traders typically trade pairings rather than a single currency's index, so they take a bullish or bearish position on the dollar relative to another currency.