There are four types of fidelity for prototypes.

The one you choose to use depends on the time you have to build it, the stage of the design process you’re in, and the feedback you’re looking for.

1. Low Fidelity

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Low-fidelity, or paper, prototypes are used when you need more clarity on whether your approach even addresses the problem to solve. They are great at obtaining early concept validation and providing a general sense of how an idea can play out. Prototypes by nature are more about showing the vision for your idea and getting a sense for its product market fit rather than the specific usability of your product. Generally, these prototypes are theatrical in nature. Since you aren’t using any digital product to transition from one state to the next, there needs to be someone playing the part of the computer for users as they test the prototype.

2. Mid Fidelity

Mid Fidelity Mid-fidelity prototypes are used to test the structure of your solution. It’s great for mid-stage concept validation, such as testing product market fit, but also good for getting a general sense of the usability for your product. Mid-fidelity prototypes are good when you have a decent idea of how a solution could play out and you want to test that structure.

3. High Fidelity

High-fidelity prototypes, or ones that have “final visuals,” are used when you want to test your final designs with users or demonstrate your final concept to your team. These are good for late-stage validation and building alignment on visually representing your ideas. Usually, these types of prototypes are more about usability than about concept validation—ideally, at this stage of the process, you’ve got a good sense as to whether your idea has good product market fit. These types of prototypes generally contain transitions and animations as well, to further convey that the product is like one you would experience in the real world.

4. Code

A fourth type of fidelity for a prototype is a coded prototype. These prototypes take in real data during a usability test and remember that data as the test continues. It’s the highest form of simulation of the real product outside of building it. These types of prototypes are rare but extremely impressive, as they end up feeling exactly like the product you intend to build. In some cases, some designers work with UX engineers whose jobs are specifically to build working, functional prototypes to test, like at Google, Amazon, or Meta. These prototypes are sometimes called “functional prototypes,” which start to lay the foundation for the code that will be used in the final product.