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 Paint10.5 s6.7 s< 2.5 s
First Input Delay530 ms340 ms< 100ms
Cumulative Layout Shift0.0370.006 0.1

Tracking scripts

All the tracking scripts on the site generated ~1 MB 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. 6 454 KB 2 3 KB 8 15 KB 4 0 B 9 7 KB 6 496 KB 7 41 KB 2 4 KB 1 339 B 1 571 B 2 1 KB 10 8 KB 6 1 KB 2 3 KB 8 62 KB 35 30 KB 3 1 KB 2 470 B 2 1 KB 2 2 KB 6 3 KB 2 1 KB 2 287 B 3 2 KB 2 1 KB 2 630 B 3 1 KB 2 2 KB


Optimise images

By optimising the following images, roughly 99 KB could be removed from the transfer size, about 1%. This would reduce the CO2 generated per page load from 1.84g grams to 1.81 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.
SUMMER_SALE_HP_MOBILE_1400x.jpg 293 KB 4% 49 KB
SUMMER_SALE_HP_MOBILE_1400x.jpg 293 KB 4% 49 KB

Subset large font files

Fonts should be subsetted to reduce the file size, improve performance, and reduce emissions. Subsetting a font involves removing any characters that are not needed for a particular use case, resulting in a smaller file size and faster page load times. Some specific reasons why fonts should be subsetted include:

  1. Reduced file size: Subsetting a font removes any unused characters, which can result in a smaller file size. This can help to reduce the amount of data that needs to be downloaded, leading to faster page load times and lower emissions.
  2. Improved performance: Fonts that are subsetted are faster to load and render than fonts that are not subsetted. This can help to improve the overall performance of a website, leading to a better user experience.

Overall, subsetting fonts is a good practice for anyone looking to optimize the performance and reduce the emissions of a website of a website.

centurygothic_n4.ad57dd3bb953e5ec072f848ba96048738158e9b0.woff2 ~20 KB ~3 KB
centurygothic_n4.ad57dd3bb953e5ec072f848ba96048738158e9b0.woff2 ~20 KB ~3 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.

Replace jQuery and jQuery libraries with more modern code

jQuery is a popular and widely-used JavaScript library that simplifies web development by providing a set of tools and functions to interact with HTML documents, handle events, create animations, and make asynchronous HTTP requests.

In the past, jQuery was a very popular choice for web development because it simplified many common tasks and provided a consistent and cross-browser-compatible API. However, with the advancement of modern web technologies and improvements in browser capabilities, the need for jQuery has decreased.

Many modern web frameworks and libraries, such as React and Angular, provide their own set of tools for handling common tasks and interacting with the DOM, making jQuery less necessary in many cases. The Javascript engine in modern browsers have also become more consistent in the feature implementations often eliminating the need for a library like jQuery.

jQuery represents an opportunity because:

  1. Performance: While jQuery is a powerful and useful library, it can slow down website performance due to its large size and complex code. Modern browsers have also improved their native support for many of the features that jQuery provides, reducing the need for it.
  2. Maintainability: jQuery code can be difficult to maintain and update, particularly as web technologies evolve and change. This can make it harder for developers to keep up with best practices and standards for web development.
  3. Accessibility: Some jQuery plugins and features can create accessibility issues, particularly for users who rely on assistive technologies. This can make it harder for people with disabilities to use and access websites.

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.
Timing4.7 s1.8 s

Largest Contentful Paint

Timing10.5 s6.7 s

Total Blocking Time

Timing1,500 ms580 ms

Speed Index

Timing10.3 s3.7 s

Time to Interactive

Timing24.2 s8.5 s

Max Potential First Input Delay

Timing530 ms340 ms

First Meaningful Paint

Timing4.7 s1.9 s

Eliminate render-blocking resources

InsightPotential savings of 3,260 msPotential savings of 320 ms

Properly size images

InsightPotential savings of 42 KiBPotential savings of 61 KiB

Defer offscreen images

InsightPotential savings of 154 KiBPotential savings of 583 KiB

Minify JavaScript

InsightPotential savings of 22 KiBPotential savings of 22 KiB

Reduce unused CSS

InsightPotential savings of 49 KiBPotential savings of 51 KiB

Reduce unused JavaScript

InsightPotential savings of 817 KiBPotential savings of 1,639 KiB

Enable text compression

InsightPotential savings of 35 KiBPotential savings of 35 KiB

Reduce initial server response time

InsightRoot document took 790 msRoot document took 1,720 ms

Avoid enormous network payloads

InsightTotal size was 3,600 KiBTotal size was 8,215 KiB

Serve static assets with an efficient cache policy

Insight20 resources found38 resources found

Avoid an excessive DOM size

Insight2,018 elements2,467 elements

Reduce JavaScript execution time

Timing5.0 s4.1 s

Minimize main-thread work

Timing8.0 s6.6 s

Ensure text remains visible during webfont load


Reduce the impact of third-party code

InsightThird-party code blocked the main thread for 1,600 msThird-party code blocked the main thread for 440 ms

Does not use passive listeners to improve scrolling performance


Avoid document.write()


Image elements do not have explicit width and height