This feature can be added by navigating to Settings > Features > Activity > Screenshot Blur.
From there, you can toggle the default setting to apply it to your entire organization. You can also enable or disable the blur setting for individual users.
Here is how the thumbnails will appear on the Activity page if the blur setting is turned on:
Here is how the blurred image will appear:
As illustrated in the image above, when the screenshot blur enabled, it is still possible to gauge activity levels.
Hubstaff for Chromebook app also has a limitation: when using the screenshot blur option with this app, screenshots are not blurred, but images with very low quality are used instead. However, due to the nature of this approach, some texts that are written with big enough fonts, as well as some pictures may be easily distinguishable.