Measure the perceived load time (rather than actual load time)

Question

I am running a website where I have had problems with it being really slow. I believe I have made it quite speedy now with usage of caches etc.

When I click through the website myself it feels quite fast (please, try for yourself) but according to New Relic (host the website on Heroku) I have load times up to 30 sec and an average of 9 sec.

I have used tools like tools.pingdom.com to test it and it typically (depending on the load) gives a number of between 3-9 seconds (9 sec being the most common).

According to the stats at tools.pingdom.com it seems like a few external images, scripts etc are slow to load and that brings the load time stats down. That could also explain why the website actually feels fast for me. If the website is 95% loaded after 3 sec and one product image takes additional 6 secs to load, it does not really affect the user experience, in my opinion.

If that is the case, how can I check the perceived load time? Does the website feel slow to you?

Answer 1

I'd avoid averages are they are prone to outliers influencing the results - what you want is a histogram of page load times so you can tell how long the page takes to load for say 50% or 95% of visitors.

Google Analytics offers some Real User Measurement (uses Navigation Timing API which isn't supported by Safari yet)

You can find the numbers via Content > Site Speed > Page Timings and then the performance tab.

By default it uses a very low sample rate and you can increase this by adding

_gaq.push(['_setSiteSpeedSampleRate', 100]);

(Google Limits you to 10K samples a day though)

Armed with the load times, compare them against your business goals - conversions etc. - to see what effect performance is having on visitor behaviour.

EDIT

Other thing to do is use webpagetest.org and create a video of the page loading

Answer 2

In Chrome you can press F12, then go to the Network tab and reload your page. Then you should see the loading times of all resources. This is not a benchmarking per se, but it should point you in the right direction. Firefox has a similar feature but unfortunately I don't remember the shortcuts.