The thumbnail image determines what will be displayed to preview the content item in your collections, on your portfolio and in your content section.
In addition, it also determines what will be displayed as the preview if you share the content item on social media.
By default, the image that's at the top of your article will be displayed as the thumbnail (for videos and podcasts that is determined by the meta data for the respective format).
However, you can change the thumbnail anytime. Simply go to the content item in full view and select the "SEO & Social Media" panel in the sidebar.
After clicking the button labelled "Edit preview", this modal screen will open up:
You have three options from where to select a thumbnail image:
The content item: Often a content item comes with a number of different pictures, and you can select which one to use as the preview picture.
Our library: Thanks to an integration with Unsplash, you have access to a wide variety of pictures.
Your own image: You can upload a picture from your local device here.