Reading view is the default view in PowerPoint Online. It is similar to the Slide Show view in some ways because, in both views, the slide is shown in full-screen mode. However, in Reading view, you also see the PowerPoint Title Bar and the Status Bar at the top and bottom of the interface respectively, as you can see in Figure 1.
Figure 1: Reading view in PowerPoint Online
Reading view helps in quick navigation through slides. Also, Reading view is great for presentation designers who want to quickly look at their slides in full screen mode and also be in sync with other applications running at the same time.
To access Reading view, select the View tab on the Ribbon, and click the Reading View button (highlighted in red within Figure 2).
Figure 2: Reading View button
Alternatively, you can also access Reading view from the View buttons on the right side of the Status Bar, just click the third button (highlighted in red within Figure 3).
Figure 3: Reading view button on the Status bar
If you want to edit the presentation, or to run Slide Show, you can always switch from Reading view to one of the other views using the view buttons that you can see towards right on the Status Bar.
Views: Reading View in PowerPoint (Index Page)Reading View in PowerPoint 365 for Windows
Reading View in PowerPoint 365 for Mac
Reading View in PowerPoint 2019 for Windows
Reading View in PowerPoint 2016 for Windows
Reading View in PowerPoint 2013 for Windows
Reading View in PowerPoint 2010 for Windows