Aqueous Digital

What is Speed Index, and how do you improve it?

As one of the five key metrics used to determine your overall Performance score in Google’s comprehensive Lighthouse report, your website’s Speed Index (SI) score shouldn’t be overlooked.

To help you understand the importance of a good Speed Index score and how you can improve your website’s loading speed, the SEO (Search Engine Optimisation) experts at Aqueous Digital explain Google Lighthouse Speed Index more below.

What is the Google Lighthouse Speed Index?

Put simply, Speed Index is a way of measuring the page load performance of a website created by Google Lighthouse. Expressed in seconds, it measures how quickly the contents of a page are visually displayed.

A faster page load performance typically indicates a better website user experience. To calculate this score, Google uses data from the HTTP Archive to compare the Speed Index of your page with the speed indices of real websites.

However, before Google can compare your page to other websites, it needs a way of accurately determining the Speed Index of your page. To do this, Google uses Lighthouse – an automated tool designed to help improve web page quality.

This tool captures a video of your page loading in the browser and takes note of the visual development between each frame.

With a helping hand from the Speed line Node.js module, the Speed Index score for your page can then be calculated.

What is a good Speed Index?

According to Google, which uses user-friendly colour-coding to highlight your website’s Speed Index score, a good Speed Index score is between 0-3.4 seconds.

This will be colour-coded green to signify that there’s no issue with your Google Lighthouse Speed Index score.

If you receive a Speed Index score between 3.4-5.8 seconds, however, this is classed as ‘moderate’ speed and is colour-coded orange to signify as such.

A website Speed Index score of over 5.8 seconds is more of a cause for concern as this indicates particularly slow website performance.

As a result, you should be aiming for a Speed Index score between 0-3.4 seconds if you want to improve the performance of your website.

How do I fix my Speed Index?

If you have a moderate or even a low Google Lighthouse Speed Index, then you may want to consider how you can improve this score.

Fortunately, Google highlights three key issues that could be substantially impacting your Speed Index score.

These include:

∙ Excessive main thread work

∙ Extended JavaScript execution time

∙ Invisible text during webfont load

By addressing any, or all, these issues (if applicable), you could significantly improve your Speed Index score. Running a diagnostic audit can help you to identify which of these issues require the most attention, helping you to prioritise and effectively distribute resources.

While your Speed Index score is important, there are also many other crucial metrics that determine how well your website is performing. To boost your overall Performance score, you may consider other page metrics such as your Total Blocking Time, Time to Interactive, and First Contentful Paint.

To identify which areas might benefit the most from some extra attention, you should explore the ‘Opportunities’ section of your Google Lighthouse report. This will help you to identify the most significant opportunities, increasing your chances of quickly improving your Performance score.

Improve your speed index with Aqueous Digital

Worried about your website performance? Regardless of whether you’re concerned about your speed index score or any other key metric in your Google Lighthouse report, don’t hesitate to contact the experienced team of SEO experts at Aqueous Digital.

Our award-winning staff specialises in SEO, content strategies, and reputation management for high-net-worth individuals. As part of our SEO services, we’ll conduct a full audit of your website to identify areas of improvement, including ways that we can increase your speed index score.

To learn more about how we can improve the performance of your website, why not arrange your free, no-obligation consultation with our knowledgeable team today

For more information about our SEO services, packages, and fees, you can either call us on 0800 285 1424 or send us your enquiry via email to

Once we’ve learned more about your specific website marketing requirements with a free website audit, we can start your SEO journey to help improve your Google Lighthouse speed index, and thereby increase your traffic, enquiries, and brand awareness.

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