Flat design became solidified as an aesthetic around 2012, and it was a little controversial at the time. Since then it’s become more popular: it’s moved from something that we used to only see in cutting-edge design spheres to the more mainstream web. In many ways that’s good, because flat interfaces are often also minimalist: very clean and uncluttered. But what can be bad about flat interfaces is that often in order to achieve that super-clean, super-flat design aesthetic, many designers will leave out important clues that tell people where they can click; where they can go in an interface. We refer to those clues as signifiers. So when those signifiers are left out altogether or when they are weakened or they’re less traditional or less noticeable or they’re less consistent with presentations of the same element on other sites, then you end up in a situation where users aren’t really sure what they can do in a web page. They are more reliant on things like placement: so maybe a user sees what’s meant to be a footer, and they think to themselves: “OK, I’ve seen groups of links at the bottom of the page before like this, so I think I can click these.” Or they’re reliant on label text: so maybe a user sees some text that looks like static text but it says ‘add to cart’, so they understand that they can click or tap it. Or maybe they’re relying on hover. We see this a lot now in testing especially when we’re testing flat UIs where users will move their mouse around the page to see if their cursor turns into a hand to see if something’s clickable, but that’s really a crutch, and of course it doesn’t transfer over to mobile. So now we see that people are guessing whether or not things are clickable and sometimes they get it right and it works OK. But sometimes they get it wrong, and then they get frustrated. So we’re seeing that this design trend is actually decreasing user efficiency. So what can you do as a designer? Just make sure you’re never sacrificing clarity in order to achieve an aesthetic. Making a website look attractive is extremely important but it has to be balanced with usability. And the surest way to know if something will be clear to your users is to actually test with them.