[hhsnopek]

Sadly a lot of people don't use the `async` attribute for script tags. We can still load fonts over CDNs, even using Cloudfront or Cloudflare for caching.

> Then there's other annoyances, like the alignment of the text, pictures, and other content suddenly shifting about, because the font has changed, or the JS from one CDN finally finished processing and decided that, no, actually, pictures should go over there.

This is because the scripts and css are so large that it takes time for the browser to render all the rules set by that site. This can easily be optimized with the right tools or throwing out dead code, even only fetching code specific to that web page. Most developers just `script` tags into their head as well and this _kills_ loading of pages more than anything (unless your css file is thousands of lines).

CDNs are meant for distributing across the globe, you're hosting your own assets without a CDN in the middle and the site is still slow, you're optimizing in the wrong place.

[mattmanser]

There are particular circumstances you can actually use 'async' though. Load order is usually important.