Commonwealth Bank of Australia

The Index


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 Paint14.8 s3.5 s< 2.5 s
First Input Delay790 ms130 ms< 100ms
Cumulative Layout Shift00.005 0.1


Optimise images

By optimising the following images, roughly 10 MB could be removed from the transfer size, about 84%. This would reduce the CO2 generated per page load from 2.75g grams to 0.44 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.
vid_0.mp4 10 MB 83% 10 MB
image.jpg 254 KB 2% 9 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-lego.woff2 KB
icomoon.woff3 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.

CBABeaconSans-ExtraBold.woff2 ~41 KB ~24 KB
CBABeaconSans-Regular.woff2 ~39 KB ~21 KB
CBABeaconSans-Italic.woff2 ~39 KB ~21 KB

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.
Timing7.0 s2.1 s

Largest Contentful Paint

Timing14.8 s3.5 s

Total Blocking Time

Timing1,230 ms130 ms

Speed Index

Timing14.8 s5.3 s

Time to Interactive

Timing13.7 s3.4 s

Max Potential First Input Delay

Timing790 ms130 ms

First Meaningful Paint

Timing7.4 s2.1 s

Eliminate render-blocking resources

InsightPotential savings of 6,760 msPotential savings of 1,910 ms

Properly size images

InsightPotential savings of 7 KiBPotential savings of 100 KiB

Reduce unused CSS

InsightPotential savings of 105 KiBPotential savings of 106 KiB

Reduce unused JavaScript

InsightPotential savings of 361 KiBPotential savings of 362 KiB

Efficiently encode images

InsightPotential savings of 51 KiBPotential savings of 51 KiB

Serve images in next-gen formats

InsightPotential savings of 239 KiBPotential savings of 446 KiB

Reduce initial server response time

InsightRoot document took 1,520 msRoot document took 1,350 ms

Avoid enormous network payloads

InsightTotal size was 11,810 KiBTotal size was 12,314 KiB

Serve static assets with an efficient cache policy

Insight64 resources found65 resources found

Avoids an excessive DOM size

Insight643 elements643 elements

JavaScript execution time

Timing3.1 s0.5 s

Minimizes main-thread work

Timing5.6 s1.5 s

Ensure text remains visible during webfont load


Avoid document.write()


Image elements do not have explicit width and height