“[Optimizing for site speed] will never go to a point where you just have a score that you optimize for and be done with it,” said Google Webmaster Trends Analyst Martin Splitt on the October 30 edition of #AskGoogleWebmasters. Splitt joined fellow webmaster trends analyst John Mueller to field four questions on the topic of site speed, tools and metrics.

Ideal page speed. “What is the ideal page speed of any content for better ranking on SERP?” asked Twitter user @rskthakur1988.

“Basically, we are categorizing pages more or less as ‘really good’ and ‘pretty bad,’ so there’s not really a threshold in between,” said Splitt, advising that site owners should just focus on making their sites fast for users instead of fixating on an ideal page speed.

In terms of actual speed metrics, Google tries to calculate the theoretical speed of a page using lab data as well as real field data from users (similar to Chrome User Experience Report data), Mueller explained.

The best speed tool. “I wonder, if a website’s mobile speed using the Test My Site tool is good and GTmetrix report scores are high, how important are high Google PageSpeed Insights scores for SEO?” asked Twitter user @olgatsimaraki.

“In general, these tools measure things in slightly different ways,” said Mueller. “So, what I usually recommend is taking these different tools, getting the data that you get back from that and using them to discover low-hanging fruit on your web pages — so, things you can easily improve to really give your page a speed bump.”

The aforementioned tools are also meant for different audiences. “Test My Site is pretty high-level, so everyone understands roughly what’s going on there, where as GTmetrix is a lot more technical and PageSpeed Insights is kind of in the middle of that, so depending on who you are catering to — who you are trying to give this report to, to get things fixed — you might use one or the other,” said Splitt.

The best page speed metric. “What is the best metric(s) to look at when deciding if page speed is ‘good’ or not? Why/why not should we focus on metrics like FCP/FMP instead of scores given by tools like PageSpeed Insights?” asked Twitter user @drewmarlier.

FCP, which stands for first contentful paint, measures the time from navigation to when the first text or image is painted. FMP, or first meaningful paint, measures the time it takes for the main content of a page to become visible.

“It’s the typical ‘it depends’ answer,” said Splitt. “If you have just a website where people are reading your content and not interacting as much, then I think first meaningful paint or first contentful paint is probably more important than first input delay or time to interactive. But if it’s a really interactive web application, where you really want people to immediately jump in and do something, then probably that metric is more important.”

“The problem with the scores is they are oversimplifying things,” said Splitt, advising that instead of focusing on a score, “use the specific insights that different tools give you to figure out where you have to improve or what isn’t going so well.”

Imperfect speed metrics. “I am testing an almost empty page on #devtools Audits (v5.1.0) it usually gives minimum results which 0.8ms for everything and 20ms for FID but sometimes it gives worse results in TTI, FCI and FID. Same page, same code. Why?” asked Twitter user @ocurcelik66.

The acronyms above refer to the following:

FID – First input delay; which measures the time between when a user first interacts with your site (i.e., when they click on something) to the time the browser is able to respond to the interaction.

TTI – Time to interactive; the amount of time it takes a page to become fully interactive.

FCI – First CPU idle; the amount of time before there’s no longer any JavaScript or other work that needs to be done by the CPU.

“First thing’s first, these measurements aren’t perfect,” Splitt prefaced, adding that there will always be some noise in the measurements.

“Don’t get too hung up on these metrics specifically. If you see that there’s a perceptible problem and there’s actually an issue that your site stays working on the main thread and doing CPU work for a minute or 20 seconds, that’s what you want to investigate. If it’s 20 milliseconds, it’s probably fine,” said Splitt.

There’s no simple answer. “You can’t break down speed into one simple number — it is a bunch of factors,” said Splitt.

“If I’m painting really quickly, but then my app is all about interaction — it’s a messenger — so I show everything, I show the message history, but if I try to answer the message I just got, and it takes me 20 seconds until I actually can tap on the input field and start typing, is that fast? Not really. But, is it so important that I can use the contact form on the bottom of a blog post within the first 10 seconds? Not necessarily, is it? So, how would you put that into a number? You don’t.”

In the example above, Splitt highlighted the importance of selecting the speed metric that most accurately reflects how speed influences your user experience. Naturally, different types of content will require varying levels of interaction by the user, which is why certain metrics are more relevant than others.

Why we should care. Overemphasizing a particular metric, or even a specific speed score, may not be the best use of your resources as Google itself does not categorize speed in such a specific manner.

Knowing what you’re measuring will allow you to select an appropriate metric to reference and tool to use so that you can improve your site’s speed in ways that will improve user experience, as opposed to pumping up a metric that doesn’t have meaningful implications for the way users interact with your pages. As with all metrics, context matters.

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