The discussion, titled ‘CLS Impacting our SEO,’ addresses a sudden increase in Cumulative Layout Shift (CLS) issues affecting SEO performance, particularly on URLs with ?page=X query strings. npearson99 reports a sharp rise in poor CLS scores in Google Search Console starting September 3rd, 2024, with over 5,000 affected URLs. The issue appears to stem from background-color animations during topic navigation, a behavior that has existed for years but is now flagged due to updated CLS measurement by Google/Chrome. david confirms the issue and explains that the animation will be removed via a fix linked here, which will improve performance and resolve CLS problems. The fix is deployed on Meta and will be applied to the user’s site. npearson99 confirms the fix is live and observes the animation has stopped, though Google Search Console has not yet updated the scores.
We see the same sudden increase in CLS failures for meta.discourse.org, starting 9th November. Digging in, it seems to be related to the way we animate the background-color of posts when you navigate into a topic. That behaviour has been the same for 5+ years, so that suggests to me that this is a change to google/chrome’s measurement of CLS, rather than a change on the Discourse side.
We’ve decided to drop the animation in question. That should improve navigation performance on lower-spec devices, as well as resolve the CLS issue.
That change will land on Meta imminently, and I’ll get it queued up for your site as well @npearson99.
