These calls can be used to upload a preview image for a channel. This image can be separately requested from our content server, but it is also included in RSS feeds. Most RSS viewers use this image then as a “channel thumbnail”. Channels don’t have a thumb by default.
Because thumbnails have to be copied to our CDN after their creation, it takes a short while (about 10 seconds) before a new thumbnail ready to show.
The thumbnail of every channel can be publicly accessed through our content server. Next to a thumbnail in the original dimensions (of the uploaded image), a number of thumbs resized to fixed widths is available.
Please use the thumbnail whose width best matches the container in which you will show the thumbs, to avoid trafficking too large files.