I’m facing a confusing issue with the PageSpeed Insights scores for my website. Yesterday, after spending the day optimizing my site, I managed to reach a performance score of 63 on mobile. I checked it multiple times throughout the evening, and it consistently showed 63, so I was confident that the optimization was stable.
However, when I checked again this morning, without making any changes to the site or its administration panel, the score dropped to 48. I haven’t touched anything overnight, so I’m baffled as to why there’s a 15-point drop in the score.
I’ve been working on this project for a week, trying to get the mobile performance score to at least 75. It feels like every time I make progress, the score drops again without any apparent reason.
Here’s what I’ve already done to optimize the site:
• Preloaded media above the fold
• Lazy-loaded media below the fold
• Added caching modules
• Minified CSS/JS files
• Preloaded essential fonts
• Deferred non-critical scripts
• Pre-connected to the server
• Used a CDN for as many resources as possible
• The client is also looking for the best CDN solution for the entire site
The website is running on Drupal 9.x.x.
What could be causing these significant score fluctuations, and what else can I do to stabilize and improve the performance?
Thanks in advance for your help!
It’s not really possible to provide a definitive answer but the most likely reason for such a score drop after consistently getting the same score, is due to the page no longer being cached at the CDN and so having to make a (more expensive) trip all the way back to the origin server. Rerunning the test a few times may mean subsequent tests are based on the cached version again.
If that is the case then this means users experiences will also be variable (depending if they’re lucky enough to get a cached page for their visit, or are the first visitor in that region for a while and so cannot benefit from caching).
In that case you need to continue optimising to give more headroom to allow even non-cached visits to be faster, or investigate with your CDN how they can cache longer.
However, overall use the score as a guidance rather than something absolutely to aim for. A score of 48-60 suggests the site could be considerably faster, based on the tests it does. But you should also check whether these tests are reflective of real world experiences by looking at the “Discover what your real users are experiencing” section at the top of PageSpeed Insights (if you have enough traffic for that to be populated). We (Google) always advise concentrating on those figures than chasing the Lighthouse number.