Intermediate results of the icon tests: Nuvola

With a series of icon tests we currently study effects on the usability of icon design. This article however does not focus on these general design effects but presents findings specific to the Nuvola icon set.


The introduction of the new Breeze icon set in KDE let us again wonder, what aspects of an icon set actually takes what impact on the usability of it. We investigated Oxygen and Tango Icons for the LibreOffice project before, but our focus then was on checking all icons of the standard tool bar. This time we focus on different icon sets and will use 13 common actions to compare them.

With this series we are going to test at least 10 different free icon sets: Breeze, Oxygen, Tango, Faenza, Nuvola, Nitrux, Elementary, Crystal Project, Humanity and Treepata. These icon sets differ on various aspects: use of color and details, flat or not and sometimes even on the metaphor used.

So, we generally want to analyze effects of icon design on the overall performance of an icon set. Statistics on this issue can obviously only be done after all icon sets have been tested. But with every test, we win some specific insights in strengths and weaknesses of each icon set tested.

In this post we share some findings about the Nuvola icon set.

The study was finished by 520 participants (drop-out rate 6%) with an average handling time of 2:11 min.

Results of Nuvola icons

Table 1 lists the aggregated quality indicators. They show how well all icons that we used for the test were suited to symbolize the different terms. It has a range from 1 (no fit) to 10 (perfect fit), whereas you would expect values of at least 9 for well represented terms.

Table 1: Quality of the icon set for different terms based on assignment ratio (percentage of missing assignments) and conspicuity (or speed of picking icons).
TermQuality Indicator

Table 2 shows a cross-table with the percentage of false associations. These are terms where the intended icon was not chosen by the users, but some other icon was.

Table 2: Cross-table of icons and terms with percentage of false associations. The direct match is inverted (1-value, e.g. 0.99 for Add) to obtain comparable data.



The Nuvola icon set reveals the similar problems with Copy and Paste icons as other icon sets did before. The metaphor for these icons simply doesn’t seem to work out well. We should try to find a better one.

Next to these two, the icons we used for Link and Open also proved to be not optimal. A lot of people were not able to assign them at all. At the same time these icons did not tend to get mixed up with other icons in the set. It has to be said though that Nuvola does not have a dedicated Link icon. To make the Nuvola test comparable with the other tests, we decided to use the Nuvola Network icon instead.

A special finding is the comparably bad performance of Remove. Does that extra line around the ‘-‘ in the icon take such a strong influence to make it not as easily recognizable? Or is this due to the green color? What do you think?

If you know how to design icons and would like to help us to identify metaphors that work better, please contact us. Also, all raw results are publicly available on our open usability platform UserWeave.

As mentioned before: These results only reflect the internal quality of the Nuvola icon set. The final interpretation will be done after all sets have been tested. So stay tuned and please participate in our follow-up tests. And, of course, feel free to discuss these findings with us.

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