We get emails every day from website owners, telling us their site is fast but slow on mobile. Nine time out of ten they’ve tested their site on Google PageSpeed Insights (PSI) and the mobile score is low.

Long story short, a low PageSpeed Score in mobile does not mean your site is slow on a mobile device. Pagespeed Insights is not a real speed test – it’s a technical checklist test. There are some important things to understand and keep in mind when it comes to the Mobile Pagespeed Score we’ve explained below.

If you’re into tech stuff, there’s a great discussion on Github here about the credibility of Lighthouse/PSI mobile score.

1. They’re testing your site on a speed limited, CPU limited connection

Mobile PageSpeed simulates at 1.6mb/second connection – that is REALLY slow in modern internet speed terms. A moderately sized page of say 1.5-2mb is going to score low on this test simply because of the amount of time that data takes to download.

The CPU limiting they do also causes sites that have even moderate amounts of javascript to be marked down heavily. The modern web runs on javascript and many WordPress themes require a javascript library called Jquery in order to render which means they automatically score lower.

They of course don’t tell you this anywhere on the report itself, it’s hidden deep in the technical documents.

2. Pagespeed Insights Isn’t a Speed Test, It’s a Technical Checklist

Pagespeed Insights is more concerned with measuring your site against a technical checklist that correlates with speed rather than the raw speed of the site itself.

The latest version of Pagespeed Insights does take into account some speed elements but it’s still largely concerned with checking boxes.

3. Geography & Location Is Ignored

PSI completely ignores geography and doesn’t take into account where your visitors are located and where your hosting is. This means its speed test is not necessarily true to the real world. If your hosting is in Australia and your customers are in Australia but the speed test elements of PSI are performed from the US then it’s not a true-to-life test.

4. Website Speed Is Not Just Your Homepage

This is something 99.9% of webmasters running speed tests completely miss – website speed is not just your homepage. Every page on your site is important when it comes to speed and testing the homepage is useful but is a bit of a 1-dimensional approach, you should probably be looking at all pages.

5. High PageSpeed Score Will Likely Not Improve Your SEO

There’s a misconception that a high PageSpeed Score means that the Google Gods will gift magical SEO rankings. This is not the case – for starters, see the previous point.

Second, to that, achieving a 100 score especially on a WordPress site is extremely difficult unless you break the render of the site OR switch to a theme that does not use jquery – this article talks through the Fastest WordPress Themes in more detail.

We’ve seen SEO consultants and webmasters spend days obsessing over Pagespeed score in the hope it will boost SEO. Your time would be better spent on other SEO tasks like optimizing your meta descriptions for CTR or optimizing your open graph tags to boost social CTR.

6. The Score Varies Wildly From Test to Test

Run multiple tests and you’ll see the score varies wildly often by 20-30 points. That’s partly a function of geography but these inconsistencies make it difficult to trust the tool.

That’s all folks!

Really hope this helped! If it did, drop me your new scores + load times via email 🙂

Cheers,
Hafiz