Often, high-fidelity wireframes are the result of validation and a natural evolution of low- and medium-fidelity wireframes.

When should you use high-fidelity wireframes?

• At the end of the design process, when you've already established how the design needs to look, and the functionality comes to the forefront of the design conversation.
• When you need to test complex user interactions. More detail allows for more accurate judgment of the UI elements.
• If you have the time and budget. High-fidelity wireframes consume a lot of design time and are more expensive to produce.
• You're working with a partner you want to impress. High-fidelity wireframes give this third party a better visualization of the final product and speaks of your professionalism.
• You're working on a personal project. When you are in charge of your own deadlines, you can decide how much time and effort you're willing to put in. High-fidelity wireframes are great for explaining your product's potential to investors.