There’s two different ways to measure how long it takes your site to load.
The first is how long it takes for all the visible content on your site to load, commonly referred to as “domComplete”.
The second is the time it takes for all the content on your site, called “fullyLoaded”.
When optimizing page load time, you want to optimize for the time until domComplete because that is how long your users will perceive your site takes to load. domComplete is the correct metric for your users' experience.
This means Autotrack does not increase the domComplete time. OTOH autotrack can increase the fullyLoaded time since loading the larger snippet is included in the fullyLoaded time.
No, Autotrack is actually very lightweight.
If you are worried about Autotrack slowing your site down, you can take advantage of our server-side Destinations which perform the event matching on our servers. Contact Us to learn more.