What Are Google Core Web Vitals And Why They Matter

Core Web Vitals are three measurements Google takes from real visits to your pages: how fast the main content appears, how quickly the page reacts, and how stable the layout is while it loads. Google uses them as one of many signals for search ranking, and they are a fair summary of how a page feels to a visitor.

This guide explains each measurement in plain terms and points to the Tirenoa settings that influence it.

In this article: The Three Measurements · How To Measure · Settings That Affect LCP · Settings That Affect INP · Settings That Affect CLS · Related

INP replaced the older First Input Delay (FID) in March 2024. If a tool or article still speaks of FID, it is out of date.

A page passes when at least 75 percent of its visits are in the good range for all three. Google measures phones and desktop computers separately; phones are usually the harder case.

PageSpeed Insights shows two things for an address: data from real visitors over the last 28 days, if the page has enough traffic, and a test run at that moment. The Run PageSpeed Insights button at the top of Tirenoa › Performance opens it for your home page. PageSpeed Insights is a Google service; the address you test is sent to Google.

Always test logged out, or in a private browser window. Logged-in users see the admin bar and uncached pages, which is slower than what visitors get. Test an inner page too, not only the home page.

• A page cache. With Tiaro Cache active (Tirenoa › Caches), the server sends finished pages without building them first. This is usually the largest single gain.
• Upload Image Format set to WebP or AVIF, and images uploaded at a sensible pixel size.
• On the image at the top of the page: Skip Lazy Loading set to Yes and, on the Image element, Fetch Priority set to High.
• Font Face Rendering set to Swap All, so text appears before the font file has arrived.
• Preload Key Fonts: the Performance Wizard recommends None unless the largest element on your page is text or an icon.
• CSS Compiling Method set to File and Enable Critical CSS.
• Enable Video Facade when a YouTube or Vimeo element is near the top of the page.

INP gets worse with the amount of script a page has to run. The goal is to load less of it.

• The Features and Elements steps of the Performance Wizard switch off parts of Tirenoa and Builder elements your site does not use.
• YouTube API Scripts, Vimeo API Scripts and Google Map Scripts off when no page needs them.
• jQuery Migrate Script set to Disable, unless another plugin needs it.
• Enable JS Compiler left on, so scripts arrive as one file.
• Enable Video Facade, so video players load only when a visitor presses play.
• Fewer plugins. The wizard’s last step shows the number of active plugins for this reason.

• Load Stylesheets In Footer left off. With it on, visitors can briefly see the page without styles.
• Image Lazy Loading set to Tirenoa. Its placeholder has the same dimensions as the image, so the space is reserved.
• Font Face Rendering: Swap All shows text earlier, but the text can move slightly when the final font arrives. Block avoids the movement at the cost of a later first display. Fewer font families and variants reduce the effect either way.
• A header built with the layout builder. The wizard recommends it when the site still uses the legacy header, because it causes less layout shift.

Note: Content added by third parties, such as cookie banners, chat widgets and embedded ads, is a frequent cause of layout shift that no theme setting can fix. Check these first when CLS is poor.

• Optimization Guide – work through all performance settings in order
• Image Format And Size Guide – images are the usual largest element
• Image Element – Skip Lazy Loading and Fetch Priority
• YouTube Element – works with the video facade