Design UX

The Illusion of Completeness

Back in the early 2000s there was a golden rule that asserted that websites were best viewed if all the content was displayed without the need of the user to scroll down.

Flash websites gave us the possibility to mimic the way a user interacts with an operating system, meaning that all the content visible was the content available. Every piece of content that went below the fold had the risk of being overlooked.

EYE4U, an amazing Flash website with all the content above the fold.

The broken paradigm

Over the years, the World Wide Web experimented a few changes that questioned the way content is revealed:

  • Different screen resolutions. As bigger and wider screen resolutions started to pull off, having 800×600 resolution websites was no longer useful.
  • Web 2.0. Social media started to flourish. Infinite scrolling was introduced and the web started to be driven by user-generated content.
  • The mobile web. Smartphones brought the habit of scrolling in a very easy and intuitive way. Touch-enabled devices made it possible and very natural to scroll for more content.

Haven’t users learned how to scroll yet?

With the irruption of all these technologies, users have learned the mechanics of scrolling and do know that some pages have content below the fold. However, they would only scroll if they have reasons to.

For a better understanding, we should consider what the Information foraging theory and the illusion of completeness have to say.

Information foraging theory, first coined at Xerox PARC, asserts that people look for information on the web in the same way animals forage for food in the wild.

Animals will decide which prey to hunt based on how easy it is to get to the prey and the effort that has to be done. In the same way, when people land on a page, they are usually “hungry” for an information need. And whether they stay or leave that page will depend on two similar factors: 1. How hard it is to get to what the user is searching for. And 2. How promising the information looks like.

If users don’t think they can find what they need, they will probably leave and keep searching.

The false floor

There are often times that even when there is important information placed above the fold, users still won’t scroll down to look for more content.

Usability testing sessions conducted by Nielsen Norman Group found that certain design patterns lead people to believe that they’ve seen all there is on a page, making this assumption from users a major usability problem.

The Illusion of completeness was first coined in 1998 by Bruce Tognazzini, one of NN/g principals at the time. The biggest culprits of this illusion are probably large hero images or images that consume the entire height of the browser window.

Mobile and desktop version of a web page with a big hero section.
Mobile and desktop view of a page using a large hero image. Example adapted from NN/g’s YouTube video.

Avoiding false floors

With that said, it is important to keep in mind that content placed above the fold is always the most discoverable and plays a vital role in making the users scroll or leave the site.

Below are three things to consider for diminishing the “false floor” effect that The Illusion of Completeness causes.

Large images used cautiously
If a page uses a hero or a big image on top, consider placing a visual clue (like an arrow for example) to tell the user there is more content below available.

Large hero image with a visual cue to indicate there's more content below the fold.
Large hero image with a visual cue to indicate there’s more content below the fold.

Cutoff thumbnails
Another visual cue that gained momentum is the use of cutoff thumbnails to indicate that there is more content to be discovered. This approach is seen on interfaces with carousel sliders, primarily on mobile apps with horizontal scrolling.

Netflix's image carousels
Mobile app with image carousels showing cutoff thumbnails.

Gaps and horizontal lines
As these can create the illusion of a “false floor”, try to reduce the vertical spacing in the cases you consider the user might be satisfied with the visible content.

Big spacing between page sections
Big spacing between page sections may create a “false floor” in some resolutions. Example adapted from NN/g website.


As technology evolves, new needs, habits and trends arise. It is important to know that even when users are used to the mechanics of scrolling, sometimes they may think that what they see on a page is all the content they have available.

Information architecture should always encompass these factors in order to provide page layouts that avoid users getting stuck in these “false floors”. Designers must help users discover all the relevant content on a web page.

Further reading

Special thanks to Amanda and Erika for their feedback on the project that sparked this research.

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