Tobias Renström
Ever since I started designing simple websites back in the late 90s, I have enjoyed bringing designs to life through code. I learned iOS development in 2010, and first designed and built an app in 2011. One those apps has got 2 millions downloads, and has been featured on the App Store as the App of the Day, and the Free App of the Week. I have been designing and building ever since.

From doing that, I have a lot of experience with high fidelity prototyping - basically building a rough but native version of an app for testing new ideas.
When to use high fidelity in prototyping?
Testing for desirability, not usability
Why would you want to build a real app to test, rather than just testing with a simple Figma prototype? In my experience, there’s a few scenarios when this can be the difference between a happy, innovative process and a painful, dragged-out one.
You want an experience that’s not completely standard
I have noticed that there’s three stages of quality control when building any type of novel digital experience. There’s the drawing stage, usually in Figma. Then there’s simulating a final design at your desk. Then there’s experiencing the real thing in a real world scenario.

A new product or feature can usually pass through the first and second stages above with flying colours, only to reveal fatal flaws at the last one. And the last stage - that’s what your customers will experience. By prototyping with high fidelity during the design process, you can actually test that last stage while you're designing. That can often be the game changer that means you'll put something out there that will blow people away.
Your experience requires live data
Low fidelity is usually fine for pure usability testing. Concept testing is fine for getting a grip on your overall vision for a product. But how do you know you’ve nailed it, if what ultimately the customer finds desirable is dependent on real data? To know that, you need to test with real data.

One example of that could be building a Chat GPT product. If you’re building a chatbot to help people manage a part of their life better, what matters will be the answers they get, how precise they are, and how they actually help. What doesn't matter as much is wether they can understand how to navigate around it.
You’re building an MVP of a new product
Building a completely new product is a high risk endeavour. Most who try it fail. And the reason so many fail is that they don’t end up solving a problem customers care about enough. If you’re in a situation like that, you need to get your product in to the hands of customers fast. A high fidelity prototype, rather than a finished product, means you can iterate months, if not years, worth of improvements in weeks.