If you've been running tests on GTmetrix lately, you may have noticed that your site speed appears to be lower (while the number of HTTP requests higher) now than before.
Is it? The answer is no. A short while ago GTmetrix changed their default speed metric. In the past GTmetrix measured how long it took to download all visual page resources - images, CSS, etc. (onload). Now GTmetrix measures the full load time (all requests completed).
It’s no secret that if you defer JS loading, the site does not become any faster from the technical standpoint (JS has to load sooner or later). But the perceived speed increases. And that’s what we’re after as site owners, and also what Google expects.
This also explains why speed as measured by Pingdom is the closest to what you see simply testing your site visually in a browser. In fact, you may notice that the speed figure on Pingdom “freezes” while the request counter is still rolling.
You can sign up for a free GTmetrix account to get access to several advanced features, including both onload and full load speed, as well as a handful of test servers around the globe on top of the default Vancouver server. There’s also a new feature - under the Timings tab you will find a step-by-step timeline breakdown, very educational and useful for identifying problem areas.