Yes, an SEO company can improve Core Web Vitals, though it usually does so in partnership with whoever maintains your website’s code. Core Web Vitals are technical performance metrics, and improving them often means changing how a page is built, loaded, and rendered. An SEO company is well placed to diagnose the problems and prioritize them, but the actual fixes may sit with a developer, a hosting provider, or a content management system.
What Core Web Vitals measure
Core Web Vitals are three specific metrics Google uses to describe a page’s real-world user experience. Largest Contentful Paint (LCP) measures loading speed, and a score of 2.5 seconds or faster is considered good. Interaction to Next Paint (INP) measures responsiveness to user input, with 200 milliseconds or less considered good. Cumulative Layout Shift (CLS) measures visual stability, meaning how much page elements move around while loading, with a score of 0.1 or less considered good.
Google evaluates these at the 75th percentile of page visits. A page passes only when at least 75 percent of real visits meet the good threshold for all three metrics. That detail matters because it means a page can feel fast on your own device and still fail when slower connections and older phones are included.
Field data versus lab data
There are two ways to look at Core Web Vitals, and an SEO company should explain both. Field data, also called real user data, comes from actual visitors and is what Google uses for assessment. It appears in the Chrome User Experience Report and in Search Console. Lab data comes from tools that simulate a page load in a controlled setting, such as Lighthouse or PageSpeed Insights. Lab data is useful for debugging because it produces a result instantly, but it does not always match what real users experience. A good SEO company diagnoses with lab tools and confirms progress with field data, since field data is the measure Google actually counts.
What an SEO company can diagnose and fix
A capable SEO company can identify which metric is failing and why. Common causes of poor LCP include slow server response times, large unoptimized images, and render-blocking scripts. Poor INP often comes from heavy JavaScript that ties up the browser when someone clicks or taps. Poor CLS is usually caused by images or ads without reserved space, or by fonts and banners that load late and push content down.
Some of these fixes fall squarely within SEO work, such as compressing and properly sizing images, setting width and height attributes, and reducing unnecessary scripts. Others require development support, such as improving server configuration, changing how a theme loads resources, or reworking third-party code. An honest SEO company will tell you clearly which items it can handle directly and which need a developer, rather than promising a perfect score it cannot control.
How much Core Web Vitals affect rankings
Core Web Vitals are a confirmed ranking signal as part of Google’s page experience signals, but they are a modest factor, not a primary one. Content quality, relevance, and how well a page matches what someone is searching for carry far more weight. In practice, Core Web Vitals tend to act as a tiebreaker. When two pages are similar in relevance and quality, the faster and more stable one can gain an edge. Improving performance alone rarely lifts a page that has a content or relevance problem.
That honest framing is worth listening for when you evaluate an SEO company. A trustworthy provider treats Core Web Vitals as one part of technical health that also benefits conversions and user satisfaction, not as a shortcut to higher rankings. Ask any company you are considering how it measures Core Web Vitals, whether it works from field data, and how it coordinates with your development team when a fix is outside its direct control. Clear answers to those questions are a good sign that the work will be both realistic and useful.