Speed is essential for menus that contain multiple levels. The more levels a menu has, the longer it takes to navigate. A common navigation pattern is a three-level menu. You’ll often find it on dashboard interfaces and desktop applications. The easiest way to optimize the navigation speed of a three-level menu is to design for the fastest layout.
A research study (A comparison of three-level menu navigation structures for web design) has shed some light on which layout is fastest to navigate. They evaluated various three-level menu layouts based on several criteria categories.
The navigation layouts include top-top-top, top-left-left, top-top-left, top-left-top, left-left-left, left-top-top, left-left-top, and left-top-left. The level notations are ordered by priority and hierarchy (i.e., primary-secondary-tertiary). The criteria categories include navigation time, user hesitation, cursor movement, selection errors, and user preference.
The study discovered that a left primary is faster to navigate than a top primary. This effect also applies to left secondary menu levels. It also found that navigation is faster when the primary level is separate from the secondary and tertiary levels. Overall, left-top-top and top-left-left were the fastest, and top-top-top and top-top-left were the slowest.
A hesitation is when the user hesitates to move their cursor from one menu level to another. The left-top-top had the least hesitation out of all the layouts, and the top-left-left had the most. There was a significant decrease in hesitation when the secondary and tertiary levels were on the same plane.
The frequency of cursor movements to the incorrect plane represented a cursor movement. There were fewer cursor movements when the primary menu was on the left. Fewer cursor movements also occurred when the secondary level was split from the primary. Many cursor movements occurred when secondary and tertiary menus were on different planes. But when they were on the same plane, users performed better.
Left-left-left and top-top-top had the fewest cursor movements, while top-top-left and top-left-top had the most. This effect makes sense because when all menu levels are on the same plane, it’s harder for users to move their cursor to the wrong plane.
The number of excessive clicks represented a selection error. When the primary level was on the left plane, the least amount of selection errors occurred. A left primary reduced selection errors by 80% compared to a top primary.
A significant number of selection errors occurred when both the primary and secondary were on the top plane. Top-top-top and top-top-left performed the worst. Fewer selection errors occurred when the secondary and tertiary levels were on a separate plane from the primary. Left-top-left and left-left-left performed the best.
The majority of users preferred using a left primary than a top one. Left-top-top and left-left-left were most preferred. There was a strong preference for grouping the primary and secondary levels and secondary and tertiary levels. Top-left-top and left-top-left were the least preferred. This effect implies that users don’t like jumping back and forth between planes.
Best vs. Worst Overall Performance
An overall score was given to each layout based on their performance for all criteria categories combined. The best performing navigation layout was left-top-top, followed by left-left-left. The two worst-performing ones were top-top-left and top-left-top. Out of the two best, left-top-top was faster than left-left-left by approximately 17 seconds.
Left-left-left is slower than left-top-top because when all the menus are on the left, it requires users to scroll through the list of items. As the levels expand and go deeper, users have to scroll more and can no longer view all the primary items on a single screen. However, the benefit left-left-left has is that users can consume more content per screen view. Users spend less time navigating the content screen, but it’s a tradeoff for more time navigating the menu.
The screen view advantage for left-top-top allows users to view more primary items at a time no matter how deep they navigate. However, they see less content per screen due to the top navigation bars. As a result, users experience less menu scrolling but more content scrolling.
No matter which navigation layout you choose, left-left-left and left-top-top are both winners. There are give-and-takes between screen view and scrolling, so it’s important to evaluate what’s more important for your UX.
If your users navigate between different primary categories a lot, go with left-top-top to minimize menu scrolling, and maximize menu viewing. If your interface displays a lot of content with large and heavy visuals (e.g., photos, videos, graphics), go with left-left-left to minimize content scrolling and maximize screen view.
It’s possible you can increase the content screen view for left-top-top and still reap the benefits of less menu scrolling. By temporarily hiding the top navigation bar when users scroll down the screen, they can get a full content view. When they scroll up, the bar will reappear. The assumption is that users are viewing content when they’re scrolling down. When they scroll up, their intention to navigate is more likely.
In my opinion, left-top-top is the winning navigation layout. Not only is it a few seconds faster than left-left-left, but it allows users to recognize which primary category they’re on. When you have multiple menu levels expanded in the left sidebar, it takes more effort to recognize which level you’re on. It’s also easier to mix up secondary and tertiary items since they’re so near each other.
A left-top-top layout makes scanning primary categories easy. It distinguishes secondary and tertiary categories from primary and places them on different vertical levels. Therefore, users are less likely to mix up secondary and tertiary items when scanning horizontally.
Of course, left-top-top isn’t the best choice for every use case and interface context because there are exceptions to every rule. But overall, it appears to perform superiorly to all other three-level menus.