Updated July 18th, 2019

PageSpeed Insights (PSI) is a web performance analysis tool developed by Google to help you optimize your website.

It’s a useful tool to find optimization opportunities. It’s one of the analyzers we use in our toolbox.

It’s not a useful scoring system for Shopify sites or complex platforms that integrate with 3rd party apps.

Why we don’t use it as a benchmark/scoring system:

  • Sometimes you implement an optimization that clearly makes your site faster, but then the score goes down 🧐
  • Sometimes you clear warnings they give, and the score goes down
  • Sometimes when comparing 2 sites, the faster site scores lower

I understand why – tools like this are complex and rely on algorithms and computer analysis based on a system of rules to calculate a score.

Clearing every warning doesn’t make sense – sometimes it’s not possible, and sometimes it can cost future maintenance or breakage without adding significant value (for example when dealing the render blocking warnings).

What PSI is good for

  • Ideas for optimization opportunities
  • Analysis of a project where you have complete control of the loaded resources
  • Keeping up to date on what areas Google is recommending for performance optimization

Example of before/after scores when implementing lazy loading

If you’re not familiar with lazy loading, it’s an optimization technique that loads images as the user scrolls, rather than all on the initial page load. If you want to implement lazy loading, check this Lazy Loading Images on Shopify article.

In this example case we implemented lazy loading on a site, making it lighter and faster, and loading fewer requests, but the Google PSI score went down.

This happens often.

Our main goal is to make your site lighter and faster, so we focus on page weight, file requests, and load speed.

The tool we’ve found most accurate for before/after metrics and setting benchmarks is webpagetest.org.

Here are the before/after stats after implementing lazy loading:

WPT metrics before

webpagetest before lazy loading

WPT metrics after

webpagetest after lazy loading

*Note on WPT scoring system: You’ll notice the key metrics improved (highlighted in the drawn boxes), but the grades went down. My theory here is that after optimizing by removing images from the page using lazy loading, the remaining factors on the page got more attention, and are now triggering additional warnings or having more weight in the scoring system.

Similar to Google PSI, the analysis reads different areas for performance, then changes the score based on the algorithm’s output – but this doesn’t necessarily correlate to actual speed.

Google PSI score before

google psi score - before lazy loading

Google PSI score after

google psi score - after lazy loading

Summary: This page has fewer server requests, is lighter in weight, and loads faster, yet the Google PSI score dropped.

BEFORE AFTER % IMPROVEMENT
Page load speed 4.12 3.59 13% faster
Page weight (DC) 1.37 MB 1.12 MB 18% lighter
Server requests (DC) 76 55 28% fewer requests
Google PSI Score (mobile) 29 15 48% score drop
Google PSI Score (desktop) 91 89 2% score drop

How to get a higher Google PSI score

If scoring higher on Google PSI is important to you, here are some ways we’ve found to increase it:

1. Setup Google AMP (Accelerated Mobile Pages).

The number 1 way to improve your PSI score is to install Google AMP.

What AMP does is create a set of lean pages that abide by Google’s AMP guidelines – then these pages get pre-cached by Google and load instantly in Google search results.

You can use the app AMP by Shop Sheriff to handle this automatically while allowing you to customize the pages.

You’ll lose some control over your page design (and apps you can use on these pages), but sometimes this is better (Google reports that AMP increases conversion rates)… also just going through this exercise will sharpen your knowledge on what lean pages look like on your site.

If you want to know more about AMP, check out our Google AMP Guide for Shopify sites.

Shopify servers are fast, and professional themes are usually well built, yet I don’t think I’ve ever seen a Shopify site score high in both mobile and desktop on Google PSI. If you know of one, please drop it in the comments 👇

2. Optimize your theme

Your PSI score often goes up after optimizing your site, but not always, as illustrated above. Lazy loading is a key optimization because it prevents images from loading on the initial page load. So definitely do that 👍

Other than that, these are some areas you can optimize:

  • Compress your images
  • Minify CSS and JavaScript
  • Scan your site for old app code that’s still loading resources, and remove it
  • Reduce the amount of apps and elements loading on the page

If you’d like more info about Google PSI see this in depth guide: The Truth About Google PageSpeed Insights for Shopify.

How to analyze and optimize a Shopify site

We built an app specifically to analyze Shopify sites – the Shopify Analyzer.

Give it a go, it’s free 😎

Shopify optimization is our wheelhouse – if you want your site optimized for you, check out our Shopify optimization services.

To get an idea on what we guarantee, and our process, take a look at this post: What to Expect.