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Development10 min read

Core Web Vitals Explained for People Who Don't Write Code

Core Web Vitals affect your search rankings and your user experience. You don't need to be a developer to understand what they measure or what you can do about them.

E
Excelle Escalada
Digital Experience Architect

A performance score that actually affects your rankings

In 2021, Google made Core Web Vitals a confirmed ranking factor in search. This means the speed and stability of your website affects where it shows up in search results — not just whether it gets crawled or whether it has good content.

Most content and communications teams know this happened. Far fewer understand what Core Web Vitals actually measure or what decisions they make that affect them.

That gap matters. Content decisions — the images you upload, the videos you embed, the amount of text you put on a page — have a direct impact on core web vitals scores. You don't need to write code to make a difference, and there are plenty of technical SEO issues content managers can fix without developer help. But you do need to understand what you're dealing with.

What Core Web Vitals measure

Google's Core Web Vitals are three specific measurements of how a page feels to use, collected from real users. They aren't simulated or theoretical; they're based on actual Chrome browser data from real visits to your site.

Largest Contentful Paint (LCP)

What it measures: How long it takes for the largest visible element on the page to load.

In plain language: The moment when the page looks "mostly loaded" to a user. Not when the first tiny thing appears, but when the biggest element (usually a hero image, a large heading, or a prominent block of text) is fully visible.

Why it matters: Users judge perceived load speed primarily by when the main content appears. An LCP of 2.5 seconds or less is considered "good." Above 4 seconds is considered "poor."

What content teams can affect:

  • Image file size and format (large, unoptimized hero images are the most common LCP culprit)
  • Whether images are in next-generation formats (WebP instead of JPEG or PNG)
  • Whether large images have loading="lazy" removed from above-the-fold images (lazy loading delays their render)
  • Interaction to Next Paint (INP)

    What it measures: How long it takes for the page to visually respond after a user interaction (a click, a tap, a keypress).

    In plain language: The delay between when a user does something and when something visibly changes. In a search box, it's the gap between typing and seeing the results update. On a button, it's the delay between clicking and seeing feedback that the click registered.

    Why it matters: An INP of 200 milliseconds or less is "good." Above 500ms is "poor." Pages with high INP feel sluggish and unresponsive even if they load quickly.

    Note: INP replaced First Input Delay (FID) as a Core Web Vital in March 2024. If older reports mention FID, that's the same concept now measured more comprehensively.

    What content teams can affect:

  • Third-party scripts (chat widgets, marketing scripts, analytics tools) added to pages increase processing load, a problem closely related to CMS plugin bloat. Every third-party tag slows INP slightly.
  • Rich interactive content embedded directly in pages can slow responsiveness.
  • Cumulative Layout Shift (CLS)

    What it measures: How much page content unexpectedly shifts position during loading.

    In plain language: The moment when you're about to click a button and an image loads above it, pushing the button down and making you accidentally click something else. That's a layout shift.

    Why it matters: CLS measures the total amount of unexpected movement on a page as it loads. A CLS of 0.1 or less is "good." Above 0.25 is "poor." High CLS is frustrating and can cause users to accidentally interact with the wrong element.

    What content teams can affect:

  • Images without defined width and height attributes shift the layout when they load (the browser doesn't know how much space to reserve)
  • Embedded content (ads, embeds, iframes) without defined dimensions cause layout shifts
  • Fonts that load late and change text size shift content
  • Why content choices affect performance more than most people realize

    Developers control the code. Content teams control the content. On most websites, content is responsible for more of the Core Web Vitals score than code quality, because:

  • Images make up the majority of page weight on most sites
  • Most LCP elements are content assets (hero images, background images, large headers)
  • CLS is overwhelmingly caused by images and embeds without defined dimensions
  • A developer can optimize the delivery pipeline perfectly, and then a content editor can upload a 4MB uncompressed JPEG and set back the entire effort.

    The content decisions that impact Core Web Vitals most

    Image hygiene

  • Resize images to their display dimensions before uploading (don't upload a 4000px wide photo if it only displays at 800px)
  • Compress images using a tool like Squoosh (free, browser-based) or TinyPNG before uploading
  • Use WebP format where your CMS supports it
  • Add descriptive alt text (this affects accessibility more than CWV, but it's part of overall image hygiene and on-page SEO best practices)
  • Never use images wider than 1600px for typical web content
  • Avoid embedding heavy third-party content

    Every YouTube embed, social media widget, and live chat script adds JavaScript that slows your page. Ask whether each embedded element is truly necessary on that specific page.

    Define dimensions for embedded content

    If your CMS or embed code allows you to specify a width and height for iframes or embedded content, always do so. This prevents CLS by letting the browser reserve the correct space before the content loads.

    How to check your site's Core Web Vitals

    PageSpeed Insights (pagespeed.web.dev) shows both lab data (simulated) and real-world data (Chromium users) for any URL. It's free and doesn't require an account.

    Google Search Console has a Core Web Vitals report under "Experience" that shows which URLs on your site have poor or needs improvement scores, and which metric is failing.

    Check your highest-traffic pages first. A poor score on a landing page that gets 80 percent of your traffic matters far more than a poor score on a seldom-visited page.


    If your Core Web Vitals scores are pulling down your search performance and you're not sure what's causing it, get in touch and we can find the highest-impact fixes specific to your site and CMS.

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