Plus/minus buttons around zoom slider or minimalist design?

Question

My web app has zoomable interface with a minimalist slider to indicate the zoom level.

http://wikibudgets.org/w/svk/bratislava/zahorska-bystrica/2016/

I was told recently that not having the buttons as part of my slider is an UX problem (without a UX study, purely as personal opinion). I tend to disagree because I believe it is pretty obvious and it is more important to keep the interface as clean as possible, but obviously I am not objective.

I know Google Maps even hid the slider by default as an indicator in their latest redesign and kept only the plus-minus buttons.

Is it even obvious that my app has zoomable interface? And if not, would the plus-minus button on the slider make any difference?

What do you think?

Answer 1

I wouldn't necessarily agree that the presence or absence of buttons wold affect the usability without doing some research.

However, + and - buttons would offer users a clue about what the slider was for and which way to move it to achieve the results they are looking for. Without these there is a higher probability that some users will be frustrated by the slider either having no explanation for it's function or not functioning they way users expect.

... and you could always throw a few different wireframes on Usability Hub with the task 'Click the interface where you would expect to be able to zoom in' to find out which combinations of sliders, buttons and symbols works best.

Answer 2

I actually couldn't find the slider at first. When I tried to use it, it was difficult to find the right level - the scale was extreme and skewed. A clickable +- would have helped to solve both those problems. Additionally, I hate trying to "guess" where on a slider I'm trying to find - it's very frustrating not being able to click a +/- to nudge the right level. This is especially true for scroll bars, but zoom levels, volume controls, and other sliders come a close second. Like your Google Maps example, I'd actually eliminate the scroll and just replace it with mobile friendly sized +- buttons.

(While you didn't ask about it - the slider is a bit narrow and hard to click as well.)