Thanks for your interest.
The Sketchfab viewer can be embedded in any HTML-capable website: a personal site, a Tumblr blog, etc.
That said, a lot of platforms are stricter about the kinds of media you can embed. For example, you can't just post raw HTML into Facebook. We build partnerships and plugins to allow Sketchfab models in these kinds of platforms - forums, portfolios, social networks, etc. In other cases, it's more about ease-of-use. Take this forum: copy/pasting the model URL ( https://sketchfab.com/models/442c548d94744641ba279ae94b5f45ec ) to become this:
Is much more user-friendly than dealing with the full HTML code:
<iframe width="640" height="480" itemprop="embedUrl" data="https://sketchfab.com/models/442c548d94744641ba279ae94b5f45ec/embed" src="https://sketchfab.com/models/442c548d94744641ba279ae94b5f45ec/embed" frameborder="0" allowfullscreen mozallowfullscreen="true" webkitallowfullscreen="true" onmousewheel=""></iframe>
So, the technology that powers Sketchfab works "anywhere," but certain sites must explicitely allow the embedded content or implement systems to make it easier.
I hope that helps!