I&#x27;m the creator of <a href="http:&#x2F;&#x2F;plnkr.co&#x2F;edit&#x2F;" rel="nofollow">http:&#x2F;&#x2F;plnkr.co&#x2F;edit&#x2F;</a> which is a similar (but perhaps less &#x27;professional&#x27;) online web editor.<p>One thing that I find interesting is that Mozilla has decided that browsers have moved forward far enough that hosting the preview via `blob:` urls. I&#x27;ve experimented with a similar approach but had issues where different 3rd party libraries die unexpectedly when they are not dealing with http &#x2F; https.