In-Lining CSS on First Page View

[ajm_76]

(08-01-2015 08:00 AM)mikefoskett Wrote:  Hi,

I'm curious as to what performance degradation occurs above 50kb of HTML with inlined assets?

Mike

Hi Mike,

There are a lot of caveats to any answer that might be given to your question, so for the sake of clarity I'm going to omit some things and simplify others (hopefully not overly so).

On mobile, you actually run into RTT obstacles right around 14KB. But, we've found, that at around 20KB (50 KB for desktop) is when actual performance degrades for critical metrics such as first paint/start render and above-the-fold visual completion/time to interactivity.

Further on mobile, anything above 20KB really begins to grind down page-to-page navigation, the testing for which can't be done with (as far as I know) any online tool. That said, this page-to-page navigation issue is pretty easy to mitigate with cache warming and PJAX.

Ideally, you really should inline critical assets and keep them as lean as possible for the quickest render across the widest range of scenarios and devices.

Best,
AJ
Managing Partner
WpFASTER | WordPress Optimization