In options trading, a long barrier refers to a strategy where an option is purchased, and a protective order is placed at a specified barrier level to limit potential losses. With a long barrier strategy, the trader buys an out-of-the-money option while simultaneously placing a stop-loss order at a predefined price level (the barrier). This strategy is commonly employed with barrier options, such as binary options, where the potential profit and risk are predefined and contingent upon the underlying asset price reaching or not reaching the barrier level. For example, in a long call barrier strategy, the investor sets a barrier level above the current market price and buys an out-of-the-money call option. If the underlying asset price rises above the barrier level at expiry, the call option will become in-the-money, and the trader can exercise it for profit. However, if the price stays below the barrier, the option will expire worthless, and the investor's loss will be limited to the premium paid for the option.