Myth: Lighthouse Scores Are Used By Google for SEO

December 14, 2023

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What is Lighthouse?

Navigating the world of web development often involves seeking tools that can measure and enhance the quality of web pages. Among these tools, Lighthouse stands out as a user-friendly, open-source tool. Google's definition follows: 

Lighthouse is an open-source, automated tool for improving the quality of web pages. You can run it against any web page, public or requiring authentication. It has audits for performance, accessibility, progressive web apps, SEO, and more.

Here is a Lighthouse Report run of Google’s home page, simulated for a mobile device:

Lighthouse is a developer tool that can be run on any webpage. The person running the Lighthouse tool is the one choosing which page to run it on and what mode to run it in (simulated desktop versus simulated mobile), which are lab configurations, not real-world environments. The results are an automated audit with the goal of providing the developer suggestions on what may improve the quality of the page. As you can see from the 33-page Lighthouse Report above, which was run for the ultra-simple Google home page, the tool yields a highly detailed list of automated suggestions comprising the audit, even for a simple webpage.

The Lighthouse Zombie Myth

A zombie myth is a long-lived myth that doesn’t die, even though the myth-busting information has been widely available for a long time. And in the SEO realm, this myth is the biggest zombie of them all. Ask 100 marketers or people in the SEO field, “Is Google’s Lighthouse score used for search ranking?”, and you’ll be surprised at the number of people who answer ‘yes’.

No, Google does not use scores from third-party SEO tools or services. It doesn’t matter whether it’s about a website’s authority or a rating about spamminess, Google doesn’t use these scores at all." -John Mueller

The results of running the Lighthouse tool are not used by Google search. Here is one of Google's experts confirming that even though this zombie myth continues to live on, it is not true.

Chrome’s Lighthouse tool also creates scores. Google doesn’t use these scores for search either. -John Mueller

So What Does Google Use?

In actuality, Google is very clear in their documentation that SEO ranking and search appearance are based on the user's page experience, not Googlebot's crawled experience. Google measures the user’s page experience through multiple metrics named Core Web Vitals, which are derived from real user data captured from Chromium browsers around the world using the site (CrUX report).

Core Web Vitals

Core Web Vitals is a set of metrics that measure real-world user experience for loading performance, interactivity, and visual stability of the page. We highly recommend site owners achieve good Core Web Vitals for success with Search and to ensure a great user experience generally.- Google

Chrome User Experience Report (CrUX)

The Chrome User Experience Report (also known as the Chrome UX Report, or CrUX for short) is a dataset that reflects how real-world Chrome users experience popular destinations on the web.
CrUX is the official dataset of the Web Vitals program. All user-centric Core Web Vitals metrics are represented.
CrUX data is collected from real browsers around the world, based on certain browser options which determine user eligibility. A set of dimensions and metrics are collected which allow site owners to determine how users experience their sites.
The data collected by CrUX is available publicly through a number of tools and is used by Google Search to inform the page experience ranking factor.
Not all origins or pages are represented in the dataset. There are separate eligibility criteria for origins and pages, primarily that they must be publicly discoverable and there must be a large enough number of visitors in order to create a statistically significant dataset.

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