Which CDNs they are using?

Which CDNs are your favourite websites using?

Based on HTTP Archive, on an average webpage we have today:
-1855KB of content size
-97 HTTP requests/objects
-17 domains

As webpage size and number of objects increase, we have longer waterfall diagrams. By studying the waterfall diagram, we can know what are the domains and where are there servers, and then we can figure out which CDNs the website is using (or no CDN).

CDN Planet – CDN Finder is a great tool which makes life easier. Just input the URL then it will check/guess which CDN a webpage is using.

Take http://www.gov.hk as an example, CDN Finder says: “We believe the site http://www.gov.hk is using EdgeCast as a CDN.”

Use this tool to check the Alexa top 25 websites in Hong Kong, Taiwan and US. Then we have the marketshare from six CDN providers of the Alexa top 25 websites in these three markets:

Akamai 50% 36% 36%
EdgeCast 6% 18% 18%
Limelight 6% 0% 5%
Level3 0% 0% 5%
Cloudfront 6% 0% 9%
Cloudflare 6% 18% 5%
others 25% 27% 23%

However, this table is just a rough estimation only.



Since more and more websites adopt multi-CDN strategy to improve performance, sometime we should review the results in details to figure out which CDNs are being used.

Take http://www.pixnet.net as an example. It is the most popular social networking site in Taiwan. Alexa ranking #4 in Taiwan and #11 in Hong Kong respectively. CDN Finder says: “We believe the site http://www.pixnet.net is using Akamai as a CDN.”

Let’s dig into the details and verify the statement.

The following table is generate based on the results from CDN Finder and Webpagetest:

Count Hostname CDN Bytes
36 mainpage.pixfs.net Akamai 101662
27 imageproxy.pimg.tw Akamai 586353
13 s4.pimg.tw EdgeCast 265490
11 s5.pimg.tw EdgeCast 513516
10 s8.pimg.tw EdgeCast 272489
10 s2.pimg.tw EdgeCast 426017
9 counter.pixplug.in 2340
9 s7.pimg.tw EdgeCast 93922
8 s9.pimg.tw EdgeCast 308673
7 s6.pimg.tw EdgeCast 175496
7 af.pixnet.net 105341
7 s1.pimg.tw EdgeCast 123025
6 stats.g.doubleclick.net Google 19384
6 s.pixfs.net Akamai 13205
4 s.pimg.tw EdgeCast 170437
4 libs.pixfs.net Akamai 18792
3 pic.pimg.tw EdgeCast 236873
2 api.pixnet.cc 1885
2 s3.pimg.tw EdgeCast 104232
2 visitor.pixplug.in 865
1 s.pixanalytics.com Akamai 785
1 ajax.googleapis.com Google 33907
1 d31qbv1cthcecs.cloudfront.net Amazon Cloudfront 1879
1 http://www.pixnet.com 134914
1 i18n.pixfs.net Akamai 3170
1 cdn.mxpnl.com Akamai 10039
1 api.mixpanel.com 411
1 ad.pixnet.net 4691
1 pixanalytics.com 851
1 d5nxst8fruw4z.cloudfront.net Amazon Cloudfront 528

The webpage size is 3644KB, with 193 HTTP objects from 29 domains. The table is summarised into this:

Count CDN Bytes Bytes % of Total
76 Akamai 734,006 20%
84 EdgeCast 2,690,170 72%
7 Google 53,291 1%
2 Cloudfront 2,407 0%
24 251,298 7%

The second table says: “We FIND the site http://www.pixnet.net is using both Akamai and EdgeCast as CDNs, with EdgeCast carries most of its traffic.


How to use tools is more important than what are the tools.


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