One SEO professional was very concerned about some page speed issues he was experiencing.
In short, he saw different numbers everywhere, from GTMetrix, to WebPageTest.org, to Lighthouse.
He was not entirely sure who to trust when it came to these numbers.
John talked about the differences between lab data and field data. He explained that with some lab testing, you will be able to gain some incremental improvements where page speed is concerned.
The main difference between lab data and field data is this: think of lab data as data based on speculative situations. Field data is everything that users actually saw.
He said that the data you see in Search Console is known as field data. He also explained that a question and answer process to yourself could help you narrow down what’s causing the page speed issues.
Are these page speed issues something we can actually fix? Or are they something that is more like a red herring that we may never be able to fix?
Could they be a quirk that occurred in the network at some point that keeps happening? Or is it really something concrete like a third-party plugin you can remove?
These are the kinds of questions that John recommends you ask yourself when it comes to diagnosing and repairing technical page speed issues.
The SEO professional then asked about GTMetrix and WebPageTest.org. It’s not easy to perform these tests again, so who do they trust?
John further explained that in the lab testing tools, things may be okay from a theoretical point of view.
However, in practice with the field data, people see something entirely different.
Even if you have perfect testing in the lab testing tools, they do make assumptions on what users might see. This is why they are so speculative in nature.
These tools can only go so far and make assumptions about what your users see. They don’t actually measure the field data, which is what you get in Google Search Console.
This happens at approximately the 7:04 mark in the video.