Mii Studio (nintendo.com)

Editing a Mii in Mii Studio

Mii Studio (Accessed at https://studio.mii.nintendo.com, requires Nintendo Account account session) is a web app for any Nintendo account user to edit their associated Miis. it was released on May 24, 2018.

Mii data

There is an article on Studio's Mii data: Mii Studio Local Storage

Miis are stored in Mii Studio using the browser's local storage. They are encoded in base64. Mii data can be extracted and loaded from this tool using Mii Studio Loader by HeyImHeroic.

Rendering

Mii Studio appears to render Mii data through layering. It uses the Canvas API to make a series of texture drawings calls with transformations.

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  Debugging Mii Studio's canvas rendering with Safari