I talk a lot about how people hold and touch their mobile devices. It’s one of my things and I have done a lot of research and speaking on it. To some acclaim, except for one thing. Occasionally, someone will get upset or disagree when I say Apple is dead wrong for saying 44px as a hit target in their design and development guidelines.
So for a change, let’s talk head-on about why I give them grief for it
- Because they say it so very much. Since I don’t really become rich and famous from this there’s not much point in me calling out Apple just to linkbait. But there’s plenty of point to calling them on it since maybe I can get accurate info out to another person who will improve their products, and spread the word further.
- They have no explanation why this is a good thing. Google, Microsoft, Nokia, ISO and others have said wrong (mostly too small) touch sizes for a long time also. But they at least base them off some interpretation of user needs and research. Some of these guidelines are based on research I did a few years back.
- It’s too small. Over time, that research has been improved on, and we’ve gotten a better picture of how people touch devices. I have personally gathered several thousand observations, and have worked with others to get even more. But I also have done a lot of meta-research, surveying the literature for other work. I’ve found dozens of research studies, all of which agree, so the guidelines I promote combine all this data and say…
- …there’s no one size. It varies across the screen (see the figure at the bottom of the page). This is actually why the old research was inaccurate and confusing, as it took a while to figure out this behavior. People are more accurate (and faster, and more confident) in the center, no matter how they hold a mobile phone or tablet.
- It conflates touch target and interference. Most guidelines do this, but it doesn’t make it right. The ability to touch a place on the screen is not the same as the need and danger of missing entirely. Some guidelines suggest a few mm between targets, but the right way is to measure on centers. Apple blows off the whole thing with a single size, and implies that targets can be adjacent to each other. They should not be.
- 44 px is not a size. This is the one that really gets to me and indicates Apple has put little or no thought into this since the very first iPhone. Because at some point they started making other screen sizes, and so 44 px varies in physical sizes widely. It is obvious on the face of it people don’t change their touch accuracy based on screen resolution. We need guidelines in physical, real-world units, and then must translate them to the individual device sizes instead.
Android is no better as they switched to a dp-based size a while ago, and that’s also a problem. But no one yells “48 dp” from the hilltops, so it’s not a as much of a problem. And with less than 2% installed base, who cares what Microsoft and Blackberry say anymore.
I am not a hater, and have lots of Apple products here, but if after all this you still look at me suspiciously, then I’ll have to just call you a fanboi. The data has spoken.