Ready Player Me
Ready Player Me is a cross-game avatar platform for Unity, Unreal Engine, and webGL. They provide a character creator, to make your own avatar, and a service to host your avatar assets at a unique url, this means you can take your avatar with you into different games and applications that support the Ready Player Me SDK.
Using Visage, open source React components designed to showcase Ready Player Me Avatars, I have my Avatar loaded as a demonstration of how to use an avatar "in game". To see your character loaded into the "game" paste the Ready Player Me Avatar url into the input and hit enter. If you don't have a Ready Player Me Avatar you can create one in the avatar creator below.
The iframe below is quick and dirty demonstration of the Ready Player Me Avatar Creator example provided when you sign up as a developer on their studio domain. After signing up and registering your game information RPM will assign a domain for you to use as a portal to access players' universal avatars, or allow them to create a new one for your game. If you already have an avatar all you have to do is sign in to choose your avatar and copy the url, otherwise you can create a new one anonymously and copy the url presented after completing creation.