To make something simple, make it predictable

One of the simplest tasks I perform every morning is turning on the lights. I flip the switch, the lights go on.

In reality, turning on the lights is actually a complicated process, probably involving solar panels, power grids, neighborhood transformers, circuit breakers, and more. But all I know is that every time I flip a light switch, the lights go on.

To make a product feel simple, every time a person takes a particular action, they should see the same result. That predictability means the user always understands their place in a product.

There’s an added bonus here: not only is predictability key to simplicity, predictability is also a substitute for control.

You can’t always give a user total control — after all, you’re designing the product, not them. But you can help them understand what will happen every time they take an action, which is almost as good.

In my house, I can’t control how the lights work without a ton of extra effort — like adding a dimmer, or customizing how much power goes to my house. But if I know that every time I flip a switch, the lights go on, I’m fully in control of whether or not I have enough light to read by.

In the same way, if I know exactly what will happen every time I hit a specific button in a product, I am in control. I can always choose exactly the action I want to take.

Of course, if I flip a switch in my house and the lights don’t go on, suddenly I’m worried. Is the power out? Did a lightbulb blow? Did I do something wrong?

When I hit a button in a product that looks like one I’ve hit before but it does something different, or when features and buttons move around unexpectedly, I start to feel like the product isn’t “mine” — and that maybe I’m at fault for not understanding how things work. It’s like someone came into my house and moved my furniture around while I was sleeping.

Sometimes those changes lead to an exciting sense of discovery — “Here’s something new for me to try!” But sometimes they lead to a sense of frustration or confusion — “Did this light switch always work this way, and I just never understood it?”

Predictability gives users a sense of control. It also gives us control as builders – so we can be intentional about where to create moments of excitement and where to focus on simplicity and ease.