Why are iframes so slow?

Question

I have little bit longer question for you - but hope answer will be very simple :)

Let\'s say I have very simple page with link and iframe (just for simple example).

Answer 1

You are pretty much on the right track. iframes are going to be slower because there is an additional overhead for the browser (rendering it, maintaining it's instance and references to it).

The ajax call is going to be a bit faster because you get the data in and you then inject it, or do whatever you want with it. The iframe will need to build an entirely new "page" in the browsers memory, and then place it in the page.