How fast is fast enough?
I’m asked this question a lot. Page weights and load times vary so much from site to site and industry to industry. While it’s easy to spot the obviously bad examples, it can be much more difficult to find the line between is “fast enough” and what is slow.
My usual answer of “make it as fast as possible” doesn’t seem to make people very happy, so let’s try to get at least a little more concrete.
Paul Irish's comment
My answer to how fast is fast enough? A Speed Index of under 1000.
And for professionals that get there, they should shoot for delivering the critical-path view (above the fold) in the first 14kb of the page. That way you are guaranteed to be serving the initial view of the site within the first RTT.
(These two goals come from a deck on perf tooling I did a bit ago)
And lastly I think most people's expectations for what's OK is currently way too lax. :)
Source: css-tricks.com