Google Lighthouse Performance

The Google Lighthouse performance score is a metric that measures the speed and performance of a website. It’s an overall score that ranges from 0 to 100 and is generated based on a number of different performance metrics, such as the time it takes for a website to load, the time it takes for a website to become interactive, the size of the resources used by the website, and other factors that impact the user experience.

A high performance score in Google Lighthouse indicates that a website is fast and responsive, which can lead to a better user experience and improved search engine rankings. On the other hand, a low performance score can indicate that a website is slow and unresponsive, and can negatively impact the user experience.

Mobile Performance
Desktop Performance

Core Web Vitals

Core Web Vitals are a set of specific factors that Google considers important in a webpage’s overall user experience. Core Web Vitals are made up of three specific page speed and user interaction measurements: Largest Contentful PaintFirst Input Delay, and Cumulative Layout Shift.

Largest Contentful Paint5.4 s1.4 s< 2.5 s
First Input Delay580 ms90 ms< 100ms
Cumulative Layout Shift0.6150.015 0.1

Tracking scripts

All the tracking scripts on the site generated ~214 KB of data

A tracking script is a code snippet designed to track the flow of visitors who visit a website. Media, advertising, and analytics organisations will provide a script to add to your website that sends data directly to their servers. This data can then be used to measure goals and conversions, analyse user behaviour, and influence advertising campaigns.

Consider how much of this data you actually need and use? How often do you review the analytics data, and does this inform genuine change? Are you actively running social media campaigns? Consider pausing or removing tracking scripts that aren’t being actively used. 2 169 KB 7 43 KB 2 1 KB 1 407 B


Optimise images

By optimising the following images, roughly 900 KB could be removed from the transfer size, about 22%. This would reduce the CO2 generated per page load from 1.06g grams to 0.83 grams.

Images should be optimised for the web for several reasons:

  1. Reduced file size: Optimizing images can result in a smaller file size, which can help to reduce the amount of data that needs to be downloaded. This can lead to faster page load times and improved performance.
  2. Improved user experience: Optimising images can help to improve the overall user experience, as pages with optimised images load faster and are more responsive.
  3. Lower emissions: Optimising images can help to reduce the emissions associated with data transfer, as less data needs to be transmitted over the network.
  4. Better accessibility: Optimising images can make them more accessible to users with slower connections or limited data plans.
rt-salt-banner.jpg 495 KB 12% 320 KB
rt-diavik-water.jpg 357 KB 9% 140 KB
rt-iron-ore.jpg 318 KB 8% 128 KB
rt-windfarm.jpg 265 KB 6% 105 KB
rt-diavik-rough-diamonds.jpg 183 KB 4% 85 KB
rt-titanium-plane.jpg 181 KB 4% 90 KB
rt-careers.jpg 49 KB 1% 20 KB
garry-parental-leave.jpg 32 KB 1% 12 KB

Replace icon font files

Font icons can have a negative impact on performance and emissions because they can increase the size of the page and the amount of data that needs to be downloaded. Some specific reasons why font icons can be bad for performance and emissions include:

  1. Increased file size: Font icons are typically included as part of a web font, which can be a large file that needs to be downloaded. This can increase the overall size of the page, leading to slower load times and higher emissions.
  2. Inefficient rendering: Web fonts are sometimes loaded and rendered inefficiently, which can result in slow performance and higher emissions.
  3. Unused icons: Font icons often include a large number of icons that may not be used on a particular page, increasing the file size and leading to inefficient use of resources.

While icon fonts are still widely used on the web, and they can be a useful tool for adding icons to a website. it is a dated practice when there are better options such as SVG icons, which can be more efficient and have a lower impact on performance and emissions.

icomoon-ttf.ttf17 KB

Remove third party font files

Font files should be loaded from the same hosting as the website because

  1. Increased loading time: Third-party sub-resources, such as scripts, fonts, or images, need to be downloaded from a separate server before they can be displayed on the website. This can increase the overall loading time of the page, leading to a slower user experience.
  2. Dependence on external servers: The loading of third-party subresources is dependent on the availability and performance of the external servers that host them. If these servers are slow or unavailable, it can result in slow page loading times or even errors.
  3. Increased risk of security threats: Third-party subresources can introduce security risks to a website, as they can contain malicious code or be used to track user activity.

First Contentful Paint

First Contentful Paint (FCP) is a performance metric that measures the time it takes for the first piece of content to be rendered on the screen when a user navigates to a web page. This content can be any visual element on the page, such as text, images, or a background color.

FCP is important because it directly affects the perceived speed of a website, and can impact user engagement and conversion rates. A faster FCP can lead to a better user experience and improved performance.

Here are a few ways you can optimise your FCP:

  1. Optimise images: Large, unoptimised images can slow down a page’s FCP. You can optimise images by compressing them, reducing their dimensions, and choosing the right format for each image.
  2. Minimise HTTP requests: Each resource requested by a web page, such as images, scripts, and stylesheets, requires a separate HTTP request. Minimising the number of HTTP requests can help to reduce the time it takes for a page to render.
  3. Prioritize critical content: Prioritizing critical content, such as above-the-fold content, can help to ensure that users see something on the screen quickly, even if the rest of the page is still loading.
  4. Reduce server response time: A slow server response time can significantly impact FCP. Optimizing server-side code and server settings can help to reduce response times and improve FCP.
  5. Use a performance monitoring tool: There are many tools available that can help you monitor your website’s performance, including FCP. These tools can help you identify performance issues and track your progress as you implement optimizations.
Timing2.5 s0.6 s

Largest Contentful Paint

Timing5.4 s1.4 s

Total Blocking Time

Timing2,230 ms120 ms

Cumulative Layout Shift


Speed Index

Timing7.7 s1.9 s

Time to Interactive

Timing13.7 s3.2 s

Max Potential First Input Delay

Timing580 ms90 ms

First Meaningful Paint

Timing2.5 s0.7 s

Eliminate render-blocking resources

InsightPotential savings of 1,480 msPotential savings of 300 ms

Properly size images

InsightPotential savings of 1,525 KiBPotential savings of 1,132 KiB

Reduce unused CSS

InsightPotential savings of 96 KiBPotential savings of 82 KiB

Reduce unused JavaScript

InsightPotential savings of 840 KiBPotential savings of 756 KiB

Efficiently encode images

InsightPotential savings of 71 KiBPotential savings of 71 KiB

Serve images in next-gen formats

InsightPotential savings of 900 KiBPotential savings of 900 KiB

Avoid enormous network payloads

InsightTotal size was 3,984 KiBTotal size was 4,110 KiB

Serve static assets with an efficient cache policy

Insight11 resources found11 resources found

Avoid an excessive DOM size

Insight1,782 elements2,259 elements

Reduce JavaScript execution time

Timing4.9 s1.4 s

Minimize main-thread work

Timing8.4 s2.4 s

Ensure text remains visible during webfont load


Minimize third-party usage

InsightThird-party code blocked the main thread for 2,420 msThird-party code blocked the main thread for 120 ms

Does not use passive listeners to improve scrolling performance


Image elements do not have explicit width and height