A gap is when a stock changes price between yesterday's close and today's open.  A gap reversal is when a stock moves in one direction between yesterday's close and today's open, then moves in the other direction after today's open.  A gap reversal alert occurs when a stock price crosses yesterday's closing price for the first time since today's open.

This alert reports the size of the gap.  The gap is defined as today's opening price minus yesterday's closing price.  This value is positive, and this is called a "gap up", if the stock price moves up between the close and the open.  This value is negative, and this is called a "gap down", if the stock price moves down between the close and the open.  If the close and the open have the same price, there is no gap, and this alert will not occur.  Note:  This is a very common definition of "gap", but this is not the only definition of gap.

This alert also reports the continuation.  If the stock gaps in one direction, then immediately starts trading in the other direction, there is no continuation.  However, if the stock gaps in one direction, then continues to trade in that direction before eventually reversing, that is called a continuation.  The size of the continuation is the amount that the stock moved in the direction of the gap, after the open, but before the reversal.

This alert will occur the instant a stock price crosses yesterday's close, even by a fraction of a penny.  Normally this alert will not occur more than once per day.  It is possible to see this more often if the exchange reports a correction to a bad print.

More options related to these alerts are listed below.