The Relative Vigor Index (RVI) indicator is a useful tool for Forex traders. This popular indicator is available for free on the MT5 platform and is used to measure the strength of a trend. The RVI is calculated by comparing the closing price of a period to the opening price of the same period, and then calculating the difference between the two. The RVI is a popular and reliable indicator for Forex traders and can be a valuable tool in any trading strategy.