Core Web Vitals: What Google Is Grading Your Site On
Google gives your website a report card. It measures how fast your pages load, how quickly they respond to interaction, and how stable they look while loading. These three measurements are called Core Web Vitals, and Google uses them as a ranking signal.
The good news: you do not need to be a developer to understand them. The bad news: most business owners have never checked theirs. Here is what each metric means, how to check your scores, and what to do if they need improvement.
Quick Navigation
- What Are Core Web Vitals?
- The Three Metrics Explained
- How to Check Your Scores
- What Good Scores Look Like
- How Much Do Core Web Vitals Affect Rankings?
- Common Problems and Quick Fixes
- How Brass-SEO Helps
- Frequently Asked Questions
What Are Core Web Vitals?
Core Web Vitals are three specific metrics that Google uses to measure how users experience your web pages. They were introduced as a ranking factor in 2021 and have been part of Google's page experience signals since.
Think of them as three questions Google asks about every page:
- How fast does the main content appear? (Loading)
- How quickly does the page respond when someone interacts? (Interactivity)
- Does the page jump around while loading? (Visual stability)
Google collects this data from real Chrome users who visit your site. This is called "field data" and it reflects actual user experience, not just lab measurements. You can see your field data in Google Search Console under the Core Web Vitals report.
The Three Metrics Explained
Largest Contentful Paint (LCP)
What it measures: How long it takes for the biggest visible element on the page to load. This is usually a hero image, a large text block, or a video thumbnail.
Why it matters: LCP is what users perceive as the page "loading." If a page takes 5 seconds before the main content appears, most people leave. Fast LCP means visitors see your content quickly.
What causes slow LCP:
- Large, uncompressed images
- Slow server response times
- Render-blocking JavaScript or CSS
- Slow third-party scripts (chat widgets, analytics, ads)
| LCP Score | Rating |
|---|---|
| Under 2.5 seconds | Good |
| 2.5 to 4 seconds | Needs improvement |
| Over 4 seconds | Poor |
Interaction to Next Paint (INP)
What it measures: How quickly the page responds when a user interacts with it — clicking a button, tapping a link, or typing in a field. INP measures the delay between the interaction and the visual response.
Why it matters: If someone clicks a "Buy Now" button and nothing happens for 500 milliseconds, it feels broken. Fast INP means the page feels responsive and alive.
What causes slow INP:
- Heavy JavaScript running during interaction
- Long tasks blocking the main thread
- Too many event listeners competing for resources
- Complex page re-renders triggered by user actions
| INP Score | Rating |
|---|---|
| Under 200 milliseconds | Good |
| 200 to 500 milliseconds | Needs improvement |
| Over 500 milliseconds | Poor |
Cumulative Layout Shift (CLS)
What it measures: How much the page layout moves around while loading. If you have ever tried to click a link and the page suddenly shifted, causing you to click an ad instead — that is a layout shift.
Why it matters: Layout shifts are annoying and erode trust. They make your site feel unstable and can cause users to accidentally click the wrong thing.
What causes high CLS:
- Images without specified width and height
- Ads or embeds that load late and push content down
- Fonts that load late and change text size
- Content injected above existing content
| CLS Score | Rating |
|---|---|
| Under 0.1 | Good |
| 0.1 to 0.25 | Needs improvement |
| Over 0.25 | Poor |
How to Check Your Scores
You have several free options:
Google PageSpeed Insights — Go to pagespeed.web.dev and enter your URL. You will see both field data (from real users) and lab data (from a simulated test). Field data is more accurate for ranking purposes.
Google Search Console — In GSC, go to Experience > Core Web Vitals. This shows your entire site's performance, grouped by URL patterns. It tells you how many pages are Good, Need Improvement, or Poor.
Chrome DevTools — Open Chrome, press F12, go to the Performance tab, and run a recording while loading your page. This is the most detailed view but requires more technical knowledge.
For most business owners, PageSpeed Insights is the simplest starting point. Test your homepage, your most important service page, and your highest-traffic blog post. Those three pages cover most of what matters.
What Good Scores Look Like
Google classifies each Core Web Vital as Good, Needs Improvement, or Poor. For your scores to count as "passing," 75% of your page visits need to fall in the Good range.
The target scores:
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| LCP | Under 2.5s | 2.5s - 4s | Over 4s |
| INP | Under 200ms | 200ms - 500ms | Over 500ms |
| CLS | Under 0.1 | 0.1 - 0.25 | Over 0.25 |
If all three metrics are in the Good range for 75% of visits, your page passes Core Web Vitals. This is the threshold Google uses for its ranking signal.
Realistic expectations: Most well-built modern websites pass on mobile and desktop without special optimization. If your site is built on WordPress, Squarespace, Shopify, or similar platforms with recent themes, you are likely fine. Problems usually come from oversized images, too many third-party scripts, or outdated themes.
How Much Do Core Web Vitals Affect Rankings?
Google has stated that Core Web Vitals are a ranking signal, but they are one of many signals. Content relevance, backlinks, and search intent still matter far more.
Here is a practical way to think about it:
- If your Core Web Vitals are Poor and your competitor's are Good, and everything else is roughly equal, they will likely outrank you.
- If your Core Web Vitals are Good but your content is thin and irrelevant, good scores will not save you.
- If your Core Web Vitals are in the "Needs Improvement" range, fixing them should be on your list but is not an emergency.
For most small businesses, Core Web Vitals are a tiebreaker, not a make-or-break factor. Focus on content quality, keyword targeting, and technical fundamentals first. Then optimize Core Web Vitals.
Common Problems and Quick Fixes
Slow LCP: Optimize Your Images
Images are the most common cause of slow LCP. Fixes:
- Compress images before uploading. Use tools like Squoosh or TinyPNG.
- Use modern formats like WebP instead of PNG or JPEG.
- Specify dimensions with width and height attributes so the browser reserves space.
- Lazy load images below the fold (but not the hero image — that needs to load immediately).
Slow INP: Reduce JavaScript
If your page feels sluggish when clicking:
- Remove unnecessary scripts. Every chat widget, analytics tracker, and social sharing button adds JavaScript. Audit what you actually need.
- Defer non-critical scripts. Scripts that are not needed for the initial page load should use
deferorasyncattributes.
High CLS: Stabilize Your Layout
If your page jumps around:
- Set image dimensions. Always include width and height on
<img>tags. - Reserve space for ads. If you display ads, set a fixed minimum height for ad containers.
- Load fonts correctly. Use
font-display: swapto prevent invisible text while fonts load.
How Brass-SEO Helps
Brass-SEO does not run Core Web Vitals tests directly, but it helps you find the pages that need attention. Ask questions like:
- "Which pages get the most organic traffic?" — Focus Core Web Vitals work on your highest-traffic pages first.
- "Which pages have the best keyword positions?" — Improving page experience on striking-distance pages could push them to page 1.
- "Are there any indexing issues?" — Technical problems sometimes overlap with performance issues.
For page-level SEO analysis including title tags, headings, and content quality, use the page audit feature. Combined with Core Web Vitals data from PageSpeed Insights, you get a complete picture of each page's health.
For a broader look at how to tell if your SEO is working, page speed is one of several factors to monitor alongside traffic trends and keyword positions.
For Squarespace-specific Core Web Vitals workarounds (the structural speed gap and what to do about it), see Squarespace SEO: Working Around the Limits.
Frequently Asked Questions
Do I need perfect Core Web Vitals scores to rank well?
No. Google does not require perfect scores. Your pages need 75% of visits in the Good range for each metric to pass. And even pages that do not pass can rank well if their content strongly matches the search intent. Core Web Vitals are one signal among hundreds. Focus on getting to Good, not on chasing a perfect 100 score in PageSpeed Insights.
My PageSpeed Insights score is low but my site feels fast. What gives?
PageSpeed Insights simulates a mid-tier mobile device on a slow connection. Your experience on a desktop with fast internet will feel much faster. The simulated score reflects what your slowest visitors experience. Look at the Field Data section (not Lab Data) for a more accurate picture of real user experience.
Do Core Web Vitals affect all types of searches equally?
Core Web Vitals are a page experience signal that applies to all search results. However, their weight relative to other factors varies. For highly competitive searches where many pages have similar content quality, page experience can be the tiebreaker. For niche searches where only a few pages answer the query, content relevance dominates regardless of page speed.
How often does Google update Core Web Vitals data?
Google collects Core Web Vitals data continuously from Chrome users and updates the dataset monthly in the Chrome User Experience Report. Changes you make to improve performance will take about 28 days to reflect in field data. PageSpeed Insights lab data updates instantly with each test.
Should I hire a developer to fix Core Web Vitals?
It depends on the issues. Image compression and lazy loading can be done without a developer using website platform settings or plugins. JavaScript optimization and render-blocking resource fixes typically need a developer. If your scores are in the Poor range, a developer can usually fix the biggest issues in a few hours. If your scores are in the Needs Improvement range, the effort may not be worthwhile unless you are in a competitive niche.