What are Core Web Vitals?
Core Web Vitals are Google's way of measuring whether a page feels fast and stable to the person using it. There are three: how quickly the main content shows up, how quickly the page reacts to taps, and whether things jump around while it loads. Google also tracks a few supporting measurements that help explain the main three.
Below, each one is explained the way our reports describe it, with the technical name, what it means for a shopper, and the target Google publishes.
Main photo shows
Largest Contentful Paint (LCP)
When the biggest thing on the first screen finishes showing, usually the hero photo, a vehicle image or the main headline. Until then the shopper is mostly looking at an unfinished page.
Google's target: Good: 2.5 seconds or less. Needs work: up to 4 seconds. Poor: over 4 seconds.
On dealer sites this is often a large hero slider image. Resizing it for phones, using a modern image format, and loading it first usually helps the most.
Taps respond
Interaction to Next Paint (INP)
How long the page takes to visibly react after a shopper taps a button, opens a filter or types in a search box. Only real visitors can measure this, so it appears in the real-visitor section of the report.
Google's target: Good: 200 milliseconds or less. Needs work: up to 500 milliseconds. Poor: over 500 milliseconds.
Inventory filters, chat widgets and tracking scripts that run a lot of code are common causes. Trimming or delaying outside scripts often improves it.
Page stays still
Cumulative Layout Shift (CLS)
How much things move around while the page loads. When a banner or image pops in late and pushes everything down, shoppers tap the wrong thing.
Google's target: Good: 0.1 or less. Needs work: up to 0.25. Poor: over 0.25. (This one is a score, not a time.)
Images without set sizes, late-loading promo banners and cookie bars are usual suspects. Reserving space for them stops the jumping.
Something appears
First Contentful Paint (FCP)
When the first text or image appears, so the shopper knows the page is loading. Before this moment they are looking at a blank screen.
Google's target: Good: 1.8 seconds or less. Needs work: up to 3 seconds. Poor: over 3 seconds.
Stylesheets, fonts and scripts that must load before anything is drawn are the usual cause. The report lists render-blocking files as a fix when Google finds them.
Server answers
Time to First Byte (TTFB)
How long your web server takes to start sending the page. Everything else waits for this, so a slow server makes every other number worse.
Google's target: Good: 0.8 seconds or less. Needs work: up to 1.8 seconds. Poor: over 1.8 seconds.
Hosting, server-side caching and how many redirects happen before the homepage loads all play a part. This is usually something your website provider controls.
Phone is frozen
Total Blocking Time (TBT)
How long scripts kept the phone too busy to respond while the page loaded. It is a lab measurement that stands in for 'Taps respond' when there is no real-visitor data.
Google's target: Good in Google's lab test: 200 milliseconds or less on a phone.
Chat, review, tracking and inventory widgets that each run their own code add up quickly. The outside-scripts table in the report shows which ones keep the phone busiest.
Source: Google's web.dev guide to Web Vitals
Questions
Are Core Web Vitals a Google ranking factor?
Google says page experience, including Core Web Vitals, is one of many things its systems consider. Good content still matters most, but a fast, stable page helps shoppers either way.
Why do lab results and real-visitor results differ?
The lab test is one simulated visit on a mid-range phone. Real-visitor data is a 28-day summary of actual Chrome users on their own phones and networks. Both are useful; they answer slightly different questions.
Why is there no real-visitor data for my site?
Google only publishes it when enough Chrome users visited in the last 28 days. That's common for local businesses, and the lab test is a good stand-in.
Which number should I fix first?
Start with whatever the report marks Poor, usually 'Main photo shows' or 'Phone is frozen' on dealer sites. The top three fixes in each report are ordered by how much time Google estimates they save.