Related article:
​How do I find my stats for my webinar?
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To find drop offs, you can go to your stats and then go to the section where it says, "Viewer Progress". "Viewer Progress" shows you a graph of what percentage of users that logged in were viewing the webinar at each progress marker. We call these minute marker. You can take your mouse on the progress marker and see the minute marker like this

Each minute marker counts the 60 seconds starting at that point, so 0min shows the number of people from 0:00 to 0:59. If your webinar is long, like the one above, you will not see every minute marker labels. But just by hovering over the graph, you will be able to see number of people at each point. 

Also, you will be able to see how many people attended your webinar every 10 minutes if you go to "Attendee Viewership" section.
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