Forex or Futures

Even though both the Forex markets and the currency futures markets are based upon the same underlying financial markets, there are some significant differences that make one or the other the best choice for day trading. 

The Forex markets have very large liquidity (amount of money traded) so they can absorb very large trades (millions of dollars) without the market being affected, whereas the currency futures can only absorb a certain number of contracts (usually less than 100) before the market becomes affected by the trade. 

On the other hand, the currency futures markets are regulated markets, so they are not susceptible to price fixing (also known as market making).

Unless you have several million dollars that you want to trade with, or you want to convert one currency to another indefintely (i.e. not convert it back again), the currency futures markets are the best choice for individual day traders. 

The two most popular currency futures markets are the EUR (Euro to US Dollar futures market), and the GBP (British Pound to US Dollar futures market), and complete information about these (and other) markets (including their contract specifications) can be found in their market profiles.