Edge cases can be difficult—even impossible—to define. Thankfully there are strategies to spotlight where edge cases are likely to hide, and you can use these strategies without changing much of your existing design process.
Of course, considering edge cases matters because what inevitably happens when they're ignored is something, somewhere in what’s built gets overlooked. And when a product is built without consideration for how it might stretch, break, or be abused, those using the product are the ones who suffer most.
We should strive to be aware of the far edges of possibilities, quite literally the edges, in order to make more informed design decisions.
When we design, we should consider anything that can be big to be colossal, and anything that can be small as being microscopic.
A text input field will need to work for one input character or 10,000. A button will need to work for a twelve character label and the 80 character equivalent in another language. A nice 14 point type paragraph on our screen might be viewed at a super high resolution to appear as though it’s just 11 point, it may also be viewed by someone with their browser base font size set to 120 points. A tab structure will need to support one single tab and maybe three dozen in the future. A drop-down menu will need to account for a single item or maybe 25,000.
We should consider scale outside of visual decisions as well: a user may navigate one screen in our product while another person buries themselves 100 screens deep. In either case: how do we help those users navigate where they need to go? How do we communicate where they are in the experience? Or consider how a user may want to upload a single photo or 40,500. The product may generate one message or error as part of a workflow or possibly 200.
When designing for a digital app that relies on touch input, some users won't have the ability to use touch. Others may have extreme touch sensitivity.
The same goes for being able to see and read the screen: according to some reports more than 10% of the global population have some variation of colorblindness. The World Health Organization estimates 1.3 billion people around the globe have some form of visual impairment, ranging from distance related problems to totally blindness
How do we ensure our products are easily digestible for the person who experiences debilitating migraines and can only consume digital experiences in daily micro doses? What can our designs do to help those who may rely on their eyes to navigate and interact with technology rather than their hands? How do we ensure things like auto-playing videos work effectively for those with hearing impairment or whose hearing is overly sensitive?
In 2015 there were 24,000 unique devices—phones, tablets, etc.—running the Android operating system. Today that number is much, much larger. A product team may be building for one or two OSes, but how many unique device types are they building for? If you’re building for Android—as an example—the number is more than 24,000. For iOS, it’s more than 20.