How many images should be updated or rotated in on a slideshow carousel that features things like products or articles?
Most people seem to agree on the common sense of a maximum around 5 images, but agree that less is better where possible. Jakob Neilsen suggests 5 because:
it’s unlikely users will engage with more than that. It can be taxing to swipe through many frames on a mobile device, and it’s difficult for users to recognize topics they have already viewed when a set exceeds about five. Limiting the number also helps with discovering the content, and finding the content in the carousel again later.
I found a similar question for mobile sites, which unfortunately also did not have a definitive answer:
As I expected, the answer given for this question also indicates that the maximum number of slides should be as many as an average user would view at one time. I would expect this number to be about 4-6, but I couldn't find a specific number anywhere. This would probably require user testing as the content of the slides would greatly affect this. For example, slides with more text and information should be shown for longer (and I have seen many sites that do this terribly) and there should probably be less slides as it involves more effort on the user's part to view each one. A carousel with single images can scroll more quickly and therefore should include more, as a user will reach the end sooner.
In my searching, I also found this great resource that may be helpful for you as you are designing your carousel:
I think I read you should automatically load no more than three images. Don Norman or Jakob Nielsen made the suggestion, but I can't find the report again on their websites.
Edit: Why is this being down voted? Let me clarify. I can't find the report again on their websites. I was having a bad user experience. The answer is 3.