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Tuesday
Jun072011

How to measure the performance of the Top 100 UK e-tailers in 11min 28secs.

Every 6 months Experian Hitwise publishes it’s “Hot Shops” list – the Top 100 e-retailers in the UK, neatly ranked in order by site traffic.

I thought it would be interesting to measure the performance of the UK Top 100 to get a sense of the “state of the art” amongst the retailers who really should be looking to optimise their site performance.

Luckily, Experian Hitwise gives you the opportunity to register and download a PDF containing the list, which you can then extract into Excel to get the list in a usable format.

So, I’ve got a list… now what’s the best way to measure the performance of 100 pages?

Well, I could use webpagetest.org and either manually test each one or use some of the scripting functions to automate it, but luckily I have access to an easier way to do it – a commercial tool by Site Confidence called Performance Analyser.

I say “luckily” but it’s not luck – I spent 6 months last year working with the team within Site Confidence that built the tool, hence it has all the cool features I wanted to enable me to move beyond “single page” analysis.

Performance Analyser can test a single page, a group of pages, or crawl your website (to some arbitrary depth or number of pages), and it can do it cross-browser (IE6, IE7, IE8, FF 2, FF3, FF3.6, FF4).

So… paste the list into the “multi-test” option, pick my browser, hit “run test” and go get a coffee and wait for the “completed” email to appear in my Inbox, which is does just under 12mins later!

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Name

Experian Hitwise Top 100 e-Retailers May 2011 #4 FF3.6

Created at

2011-06-07 13:47:57 UTC

Completed at

2011-06-07 13:59:25 UTC

Job Owner

Stephen Thair

Type of Test

Multi Page

Type of Run

Self Run


So, what information do I get?

Well, I get some nice summary graphs by size, speed and a nice combo of size/speed.

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I can also get the information as text data, which I can then export out as CSV.

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You can also get an “all objects” view, which is great for finding those ridiculously large objects. In the screen shot below I have filtered it to only show “image” MIME types and you can see the largest item across the 100 pages tested was a 382K image on the Monsoon.co.uk website.

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So lets drill down into a test so let’s look at that large spike on the size vs speed graph. I can click through on the graph and find out exactly what what site was affected, and I can see it was www.matalan.co.uk.

The waterfall graphs shows an obvious problem  - two request which failed to connect.

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In fact, we can click through and find out more details about the suspect object and get the URL(s) - https://isisaccreditation.imrg.org/8025745000669E37/accredited_idis.gif and https://isisaccreditation.imrg.org/8025745000669E37/accredited_isis.gif.

It turns out that they are 3rd party “accreditation” seals that are in the Matalan footer that are slowing down the firing of the onLoad event. An easy fix there then!

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Although Matalan could do with some domain sharding…

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As well as some “combining files” too, since they have 14 Javascript files, about 30 images files and 5 CSS files!

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If we drill down into the HTTP headers for the base HTML page we can see that it’s compressed and that they’ve set some cache control headers, albeit with no validator (last-modified or eTag), and the presence of “Pragma:no-cache” might indicate some degree of confusion…

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So what is the average performance of the UK Top 100 retailers (at 2Mbps on Firefox 3.6)?

  Min Average Max
Total Time (sec) 0.89 4.89 19.23
Page Size (Bytes)            83,000         675,007         1,829,590
Object Count 14 83 283

 

And what’s the performance difference in Firefox 4? Well, the average time is 4.58 vs 4.89. So in the “real world” the performance difference is only (4.89-4.58)/4.89=6.3%.

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