Archived topic
Sudden drop in speed on web core vitals?
3 replies · Started by Dave on June 8, 2021
Hi All,
I'm trying to wrap my brain around why my speed according to WCV has tanked. Any ideas? I've not changed themes or servers. I did some regular plugin maintenance/updates like WP Rocket, but have since rolled back to see if that's the problem. I also switched from a DO Cloudways Server to a Vultr HF, just to test as I had recently onboarding very small sites. No difference. Using Cloudflare Paid w/ Argo + ShortPixel + WP Rocket on a GeneratePress bare bones theme. GTMetrix is nearly perfect: https://gtmetrix.com/reports/bigcupofcoffee.com/z1zKW1sX/ while WCV is a shit-show: https://developers.google.com/speed/pagespeed/insights/?url=https%3A%2F%2Fbigcupofcoffee.com%2Fbest-dark-roast-coffee%2F
Thanks.
Hi there,
GT Metrix isn't running a mobile simulation on the site and theres a chance its testing a cached page.
Look at the PSI report. In the Film Strip the first frame being loaded is absent of any styles ( most noticeable on Desktop ). Main cause of this we see is the Optimized CSS Delivery option in WP Rocket. Unless you can manually configure this, its best to disable the option. Its also combining the CSS into one large ( 75kb ) CSS file which is render blocking. In a lot of instances its better to NOT combine CSS into large files as multiple small files can be served quicker.
Next is to run a performance report in Chrome DEV tools but for the sake of sharing heres on i ran on WebPageTest:
First of its a quite a large HTML file which is also flagged by Google PSI under Excessive DOM elements. And after the above render blocking CSS you see a LOT of JS files being served which are generating long task which in turn slows down the FC and LC paint. If possible you should identify any scripts that can be deferred so they don't block the main thread.
Hi David,
Thanks for the thorough reply, you rock. I've tracked down part of the problem is that I upgraded to WP-Rocket 3.9. I've rolled back and noticed all my manual choices for deferred JS are gone. So I've added them back and that seems to help. I'm still stumped about how I can do from a score in the 90s to 60s so quickly and fail Web Core Vitals.
Not sure what optimizations you had before - but rechecking the PSI report the largest render block is that combined CSS file of over 70kb. Might be worth disabling the combine CSS options to see if that helps.
