Jellyfish (our site optimization plugin) version 2.0 introduces some key CSS loading improvements which prioritizes pieces of CSS code critical to the display of the page above the fold. Following other page essentials, the full styles are loaded. This dramatically speeds up perceived page load for the visitor, allowing them to see content more quickly and start interacting with the page. In our testing of controlled group of sites, we are seeing fantastic results, like this!
Unfortunately, these amazing results aren’t replicated for every site. Sometimes our scores go down with the Jellyfish update because of heavy 3rd party scripts. The best way to explain this is with an analogy.
Think of how water flows through a pipe. If the water is blocked then nothing will go through. Our latest update prioritizing CSS will unblock the pipe and allow the water to flow. However, after the CSS flow loads quickly, scripts are next and too many of them creates new blockage.
In an ideal world, we wouldn’t need to load so many third party scripts, but unfortunately, that is often part of the landscape. Our next steps, to be deployed over the next couple of weeks, involves creating multiple pipes to dissipate the remaining load after the initial CSS, which will further boost site performance.
Finally, we are also working on a new tool to allow us to scan through our sites and determine load times with and without third party scripts, while not interfering with the live site at all. This will get us better data to evaluate our improvements and work with these third party providers to better optimize their code.