Google announced in 2021 that Core Web Vitals (CWV) would become a major ranking factor. Four years later, the verdict is mixed. Web performance matters, but not as much as some SEO agencies claim. And investing heavily in reducing Largest Contentful Paint (LCP) by 50ms when you ignore the fundamentals of strategic SEO is to miss the target entirely.
What are Core Web Vitals and their actual weight
Core Web Vitals measure three dimensions: LCP (main content display time), FID/INP (interaction latency), and CLS (visual stability). Google integrated these metrics into rankings from September 2024. But the weight is limited: a 2024 SEMrush study reveals CWV impacts roughly 5% of rankings for average pages, and up to 12% in highly competitive sectors (e-commerce, SaaS). Compare that to inbound links (40%), content quality (25%), topic relevance (15%), and you see where budget should go.
Confusion arises from conflating technical optimisation with SEO strategy. CWV is technical optimisation, not SEO strategy. A site can have excellent CWV but poor rankings if it lacks relevant content and quality links.
Where to invest in web performance
There are two scenarios. First, if CWV is poor (LCP > 4s, INP > 500ms, CLS > 0.25) and you face intense competition, optimisation is worthwhile. Gains can be 10 to 20 additional positions. Second, if CWV is in the “green zone” (LCP < 2.5s, INP < 200ms, CLS < 0.1), optimising further yields marginal gains: 2 to 5 positions at best.
High-impact actions include: reducing unnecessary JavaScript (40% of LCP time on average sites), optimising images (30% of LCP time), and implementing appropriate caching (20% of LCP time). They take a day or two of work, not a complete redesign.
LCP, FID, INP: common pitfalls
LCP often suffers because external fonts are loaded unnecessarily (Google Fonts without optimisation). The solution: self-host the font, reduce variants, or choose a system font. Gain: 200 to 400ms at no cost.
INP (Interaction to Next Paint) replaces FID from September 2024. Marketers still struggle to measure it properly. INP penalises sites with slow interactions (clicks, scrolling, input). A slow modal or poorly optimised infinite list can destroy INP. Content publishers that load heavy advertisements are particularly affected: ads often add 300 to 500ms of INP.
CLS is straightforward to fix: avoid dynamic content insertion (ads, notifications) that shifts layout. Best practice: reserve space for asynchronously loaded elements.
Measurement, monitoring, and ROI
To justify a CWV optimisation project, measure before and after. Google PageSpeed Insights, WebPageTest, and Lighthouse provide estimates but are imperfect. Test on real traffic with Real User Monitoring (RUM): a lightweight script that collects CWV from actual visitors. This tells you precisely which segment has poor CWV and where real SEO gains come from.
Rule of thumb: only spend if you will see a return in rankings or conversion. If your CWV is already decent and you are not on the first page of intense competition, it is a low-impact investment.
Conclusion: finding balance
Core Web Vitals are important but not the centre of gravity of SEO. They are a necessary condition for a competitive site, not a sufficient one. Before optimising CWV relentlessly, ask yourself the real question: do I have relevant content, quality links, a solid keyword strategy? If yes, invest in CWV. If no, start with strategic SEO, then optimise performance.