Screenshots are captured for a visual summary of an online meeting using a dynamically determined inactivity threshold time period. The inactivity threshold time period may be the sum of i) an average time interval between arrival times of screen update messages in a set of received screen update messages, and ii) a multiple of the standard deviation of such time intervals. If no significant updates to a shared screen occur during the inactivity threshold time period, a screenshot may be captured for the online meeting visual summary. A premature screenshot threshold time period may also be determined. If significant visual data is received during the premature screenshot threshold time period, the previously captured screenshot is replaced with an updated screenshot.