Try for free
Try for free

Web Speed Metrics and Core Web Vitals: A Complete Glossary

Feeling a tad overwhelmed by the technical jargon surrounding web speed? You're certainly not alone. Loading speed has become a crucial factor for not only visitor satisfaction but also for SEO and search ranking.

To help you navigate this complex landscape, we've crafted this comprehensive glossary at PageSpeed.ONE. We will clarify what each metric from the Core Web Vitals family signifies, as well as other technical indicators you might encounter during web optimization.

Choose the metric that intrigues you and discover: what exactly it measures, its ideal values, and how to optimize it.

Core Web Vitals (CWV)

Core Web Vitals (CWV) is Google's foundational set of metrics designed to reflect website loading speed and user experience. Let’s discover the metrics it includes, why they matter, and how to measure them.

Time To First Byte (TTFB)

TTFB indicates the speed of the server (or infrastructure), the server-side application, and also the network speed between the server and the user's browser.

First Contentful Paint (FCP)

First Contentful Paint (FCP) is a metric that measures the time from when a page starts loading to when any part of the page's content is rendered on the screen.

Largest Contentful Paint (LCP)

The world of the Largest Contentful Paint (LCP) metric is akin to the adrenaline-fuelled realm of motor racing – it's a relentless battle against time.

Interaction to Next Paint (INP)

Google introduces the new Interaction to Next Paint (INP) metric, set to replace First Input Delay (FID) in the Core Web Vitals trio by March 2024.

Cumulative Layout Shift (CLS)

Fed up with ads that push the text you're reading out of view? Annoyed when content jumps just as you’re about to click, making you click elsewhere?

Total Blocking Time (TBT)

Total Blocking Time (TBT) is a web performance metric that indicates the total duration during which a rendered page is unable to respond to user inputs.

Third-Party Blocking (3PBT)

The “Total Third-Party JavaScript Blocking Time” metric is an internal indicator from PageSpeed.ONE monitoring, enabling you to focus more on issues caused by third-party components that may degrade your interaction metric (INP).

JS Long Tasks (JSLT)

We will explain how the JS Long Tasks metric measures digital gridlocks in the form of long tasks and what these gridlocks can mean for your users and your business.

Lighthouse Score (LPS)

The Lighthouse Performance Score (LPS) is a synthetic metric used to assess website speed and performance, provided by the Lighthouse tool.

PageSpeed.ONE Score (SPS)

Introducing a single figure as a "proxy metric" for Core Web Vitals on both mobile and desktop. We call it the "PageSpeed.ONE Score" (SPS).

Can we use cookies to keep track of how you use the website?

Preferences

Can we use cookies to keep track of how you use the website?

Necessary for the site to function

Necessary cookies help make the website usable by enabling basic functions such as page navigation and access to secure areas of the website. Without these cookies, the website cannot function properly.

Personalization so you can save your settings

Default cookies allow a website to remember information that changes the way the website behaves or looks, such as your preferred language or the region you are in.

Analytics so we can improve the site

Analytical cookies help website owners understand how visitors interact with websites by anonymously collecting and reporting information.

Marketing so you can ask us questions via chat

Marketing cookies are used to track visitors across websites. The intention is to display advertisements that are relevant and engaging to the individual user, making them more valuable to publishers and third-party advertisers.