Should we improve time to first byte or Page Speed Insights score for SEO?

Question

Google posted last summer that "page speed" will impact the search result rankings also on mobile devices. But I think there is a little confusion about the term "page speed".

The test tool which Google offers is called "Page Speed Insights". Many people we are talking with, are thinking that the overall score of this tool for a particular site for example Desktop: 46/100 and Mobile: 45/100 is used for the ranking algorithm.

BUT I found a very interesting article in German language which states that only the TTFB (time to first byte) value is used and this should be optimized not all suggestions which "Page Speed Insights", further called PSI offers. Here is the link to the German article: https://raidboxes.de/google-pagespeed-insights-nytimes/#comment-405

In short terms it says that a very large site in this case "The New York Times" has a low overall score of Mobile:41 and Desktop:45. As they are used to sell reader memberships they should offer a great user experience. So, they should optimize their site. But when I call this site it is amazing fast. The overall PSI score does not reflect this behaviour. But when I believe this article the TTFB for this site is perfect. Also when I call it here from Austria it states 0.881sec.

I really like to know on which value we should focus our work for optimization not to fall in the ranking. Because as many of you already said it is not useful to implement all suggestions from the PSI site for one domain.

So, it would be real if you could clarify things here or post links to official posts from Google. What I found about this, Google always is talking about "page speed" but what exactly is this?

Answer 1

There are only two page load speed metrics that really matter:

• Time until the HTML page is delivered (without assets such as images, CSS, and JS)
• Time until the first screen of content is loaded and usable

HTML delivery time is important because it is the factor that Googlebot most directly sees. It controls how quickly Googlebot is able to crawl your site. Algorithmic ranking penalties that Google applies are almost all based on this metric.

Time until the the page is usable is important for users. Users turn away from a site that isn't quickly usable. This has indirect SEO consequences because Google notices when users are not satisfied with a site.

So how fast does your site need to be?

• Google will actively penalize sites where the HTML page isn't delivered in 7 seconds.
• Users start turning away from a site that isn't usable within 3 seconds.

So focus on users. They are much more picky than Google. You have three seconds. That breaks down to:

• 1 second to get your HTML page delivered.
• 1 second to download critical CSS, JS, and image assets.
• 1 second to allow the browser to render the page.

Since TTFB is a component of HTML page delivery, you need to optimize it to be a portion of the one second allotted for HTML delivery. Get it down to 200 to 500 ms.

All assets that are not needed for the page to start working should be lazy loaded. Most JavaScript should be loaded asynchronously. Images below the fold should have their load deferred.

With this in mind, the PageSpeed Insights score can be completely ignored. I do not believe that Google uses this score directly in rankings at all. The tool and the score can be useful. It can tell you which optimizations might be available to you. It may be able to help you prioritize which optimizations to perform. However it is a mistake to pay attention to the score only. Instead focus on making the site fast for users as your primary goal.

Also keep in mind that items beyond your control will effect your PageSpeed Insights score. I have a site that fully loads its pages in 1.2 seconds and gets a 100 for its score. However, when I enable AdSense on the page, PageSpeed insights reports that it takes 10 seconds to fully load and the score goes down to 63. This is despite the fact that the base page is fully usable after 1.2 seconds and the ads lazy load afterwards.