A Guide To Google Website Speed Test Tools

Website speed matters for two primary reasons. First, a fast-loading site is critical for converting customers. Second, Google uses site speed to rank your site in search. 

This guide dives into how site speed affects rankings and conversions, and explains how each of Google’s website speed test tools work. Additionally, it briefly touches on Google’s new Core Web Vitals, examines what each Google site speed tool measures and how to best utilize each one. 

Let’s dive in…


It’s a pretty well-established fact that customers get impatient and leave a site that doesn’t load at lightning speed. In fact, according to Kissmetrics.com

  • 47% of people expect your site to load in less than 2 seconds.
  • 40% will abandon it entirely if it takes longer than 3 seconds.
  • 85% of internet users expect a mobile site to load as fast or faster than on their desktop.

From Google:

  • People with a negative experience on mobile are 62% less likely to purchase from you in the future.
  • A 1 second delay in mobile load times can impact mobile conversions by up to 20%.

From Nielson Norman Group:

  • If an e-commerce site is making $100,000 per day, a 1 second page delay could cost you $2.5 million in lost sales every year. 

You get the idea. 

If your site takes longer than 2 seconds to load on desktop, and slower than 3 seconds on mobile (the Google recommendation on mobile on a 4G connection), you can lose nearly half of your customers before they even interact with your site. 


Here are a few key points Google has revisited time and again to underscore how the search giant thinks about site speed and web experiences in general:

  • Google is striving to make the whole web fast.
  • Focus on the user and all else will follow.
  • Fast is better than slow. 

Over the years, Google has made site speed increasingly more important through several algorithm updates, and in May 2020, the Chrome team announced Core Web Vitals, which breaks out various aspects of site speed (and user experience metrics) that will soon factor into Google search rankings.

Google breaks Core Web Vitals down as:

  • Largest Contentful Paint (LCP) — This measures perceived load speed and marks the point in the page load timeline when the page’s main content has likely loaded. This is a site speed measurement.
  • First Input Delay (FID)— This measures responsiveness and quantifies the experience users feel when trying to first interact with the page. This is a site speed measurement.
  • Cumulative Layout Shift (CLS) — This measures visual stability and quantifies the amount of unexpected layout shift of visible page content. This does not have to do specifically with site speed and will not be in-depthly addressed in this guide.

“The Largest Contentful Paint (LCP) metric reports the render time of the largest image or text block visible within the viewport. To provide a good user experience, sites should strive to have Largest Contentful Paint occur within the first 2.5 seconds of the page starting to load,” Google explains on web.dev.

First Input Delay (FID) “measures the time from when a user first interacts with a page (i.e. when they click a link, tap on a button, or use a custom, JavaScript-powered control) to the time when the browser is actually able to begin processing event handlers in response to that interaction,” Google says.

For more on Core Web Vitals, check out Google Core Web Vitals Basics: Everything You Need To Know.


Google has historically supplied some of the best tools for evaluating a website’s speed and experience, including:

Since the release of Core Web Vitals, here is how Google recommends you use these tools to address and improve other various aspects of site speed:

  1. Use Search Console’s new Core Web Vitals report to identify groups of pages that require attention.
  2. Then use PageSpeed Insights to diagnose lab and field issues on a page. 
  3. Use Lighthouse and Chrome DevTools to get actionable guidance on what to fix specifically. 
  4. Get a custom dashboard of Core Web Vitals using the updated CrUX Dashboard or new Chrome UX Report API for field data or PageSpeed Insights API for lab data.
  5. Confused by the amount of data and need direct guidance? Use web.dev/measure to measure your page and display a prioritized list for optimization.
  6. Finally, use Lighthouse CI before you deploy a change to production.

Search Console

Search Console measures more than site speed. It’s an essential tool that, as Google explains, “helps you monitor, maintain, and troubleshoot your site’s presence in Google Search results.” It helps you understand and improve how Google sees your site with specific data and recommendations.

This tool can be used to measure all three Core Web Vitals. Simply run the Core Web Vitals report to get a score and overview for each. You can rerun the report after making fixes to validate their effects.

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PageSpeed Insights

PageSpeed Insights is one of the simplest ways to get site speed analytics and can be used to measure Core Web Vitals, plus other key data. It is powered by Lighthouse and Chrome UX Report.

This test generates a PageSpeed Insights report, with a quantified score that summarizes the page’s performance (determined by the software automatically running Lighthouse). The goal should be to aim for a score of 90 or above, which is considered good; 50 to 90 needs improvement; below 50 is considered poor. 

When you type in a URL, PageSpeed Insights will also assess the Chrome User Experience Report (CrUX) dataset to provide a view of how real-world users experience the page.

It also reports the First Contentful Paint (FCP), CLS, FID and LCP metric data. Google advises an LCP of no more than 2.5 seconds and a FID of less than 100 milliseconds. For both, Google says strive for the 75th percentile across mobile and desktop devices.

To learn how to improve FID for a specific site, while still in PageSpeed Insights, you can run a full Lighthouse performance audit to get actionable steps.

Google says that the difference between Search Console and PageSpeed Insights is that the former provides site owners with an overview of groups of pages that need attention, while PageSpeed Insights helps identify per-page opportunities to improve user experience.


Lighthouse is an open-source, automated tool for improving the quality of web pages. It looks at site speed (including LCP and FID) and also measures other determining factors for site performance for how a potential user would experience a website. The audit lists specific opportunities for improving a website.

Lighthouse can be used in four different ways; the first three are more complex and made by and for developers:

Also, you can use Lighthouse CI to easily measure metrics on pull requests (when you’re evaluating proposed changes before integrating them into the production site). This is a best practice before rolling out website changes.

Chrome DevTools

Chrome DevTools runs Lighthouse and requires you to download the Chrome extension. Then you simply go to the Audit tab and check boxes for what you want to audit. Its greatest uses as a site speed checker are auditing pages that require authentication or identifying pages with Cumulative Layout Shift, one of the three Core Web Vitals. It provides reports in a user-friendly format. It also measures Total Blocking Time (TBT), which Google considers to be an excellent proxy for FID.

You also can download the Web Vitals Chrome extension to give you a real-time view of metrics on desktop.


For a simpler look at data, go to Web.dev and click Test My Site, then click “Measure.” It measures site performance and provides tips for improving the user experience. You can sign in order to track site progress over time.

Chrome User Experience Report

Chrome User Experience (CrUX) Report can be used to measure both LCP and FID and is used in the PageSpeed Insights report. It provides user experience metrics that show how real-world Chrome users experience your site (called field data) — and allows you to get speed data on your competitor’s URLs.

The new CrUX API launched on May 28, 2020, “enables site owners to quickly assess performance of their site for each Web Vital, as experienced by real-world Chrome users. The BigQuery dataset already surfaces publicly accessible histograms for all of the Core Web Vitals, and we are working on a new REST API that will make accessing both URL and origin level data simple and easy — stay tuned,” Google wrote on web.dev in August 2020.

You can capture this data by running a report, or using the CrUX Dashboard or new Chrome UX Report API. Not only does it measure the Core Web Vitals, it also measures, among others:

  • First Paint: as defined by Paint Timing API: reports time when browser first starts to render the page after navigation; the first key moment developers care about in page load.
  • First Contentful Paint: measures how long it takes the browser to render the first piece of DOM content after a user navigates to your page. 
  • DOMContentLoad: as defined by HTML specification: “reports the time when the initial HTML document has been completely loaded and parsed, without waiting for stylesheets, images, and subframes to finish loading.” 
  • Time to First Byte: “measures the duration from the user or client making an HTTP request to the first byte of the page being received by the client’s browser.”

A savvy developer or SEO professional will want to run the CrUX report to get this additional data.

Think with Google — Test My Mobile Site

Think with Google offers a site checker for mobile and a performance report including recommendations for fixing it. Even though this tool is powered by the Chrome User Experience Report, sometimes it’s advantageous to solely focus on mobile, especially if a site is slow and you want to call this out specifically.


Each of these site speed tools from Google provides different analytics into various aspects of website speed and other key user experience metrics. It’s important to understand how to use them and how they work together in order to make smart decisions about websites.

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