There is always debates over subfolders and subdomains in the seo world. And I myself could too often get lost on this---as I am writing this,www.12reads.cnis undergoing some root changes. We first build all our contents in a one single domain ,and then it comeswww.12reads.cn/wiki, which is a wiki site that aims to both strengthen and explore potentials of our 12reads domain. The kickoff rankings of this WIKI site is amazing indeed.It beat our main domain right away! But as sites grows(like we are planning to launch a question&ask site right now),we really cann't get rid of this subfolder or subdomain thing----we want to maintain a clear brand whilst we fear that a subdomain would only make life harder by doing it from scratch.

This blog post really inspired me and I would like to have it by my side to remind me the potential traps of  SUBDOMAINS(and also seehere where moz put up a wonderful illustration video to add things up based on their real life research also.):

SEO penalties of moving our blog to a subdomain

Let me start this article by confessing that we’re not SEO gurus at iwantmyname. Everything we’ve done in the last few years in terms of SEO was done with a basic understanding of the topic and by providing a good product with relevant content and landing pages. This always served us well and we were happy with our rankings overall. With that out of the way, I’d like to tell you about our experience with switching our blog to a subdomain. 

At the very beginning of July last year, we moved our blog from a subdirectory URL (iwantmyname.com/blog) to a subdomain (blog.iwantmyname.com) for better maintainability and performance with GitHub Pages’ CDN and future-proofing in case we wanted to switch to a different platform down the road. We made this decision after doing lots of research and had long discussions about how it might impact our search engine rankings, but we ultimately agreed to make the change. After all, it was 2014 and Google should be clever enough that it wouldn’t make any difference because they know the blog (subdomain or not) is part of iwantmyname, right? As Matt Cutts said in one of his webmaster videos “it’s a question which one is easier for you and whichever one makes you happier I would go and do it that way”.

While we expected an initial hit after making the subdomain switch and traffic slowly recovering, the turnaround didn’t happen after 6 months, as you can see in the following example:

From what we can tell, we did everything by the books with 301 redirects for all URLs - so what happened? Could it have been just coincidence that Google updated their algorithm and we got penalized for some reason?

One signal that Google introduced one month after us making the switch was to give SSL-secured sites a little ranking boost. Sinceour blog is running on GitHub Pages, whichdoesn’t currently support HTTPS, could that have prevented the traffic from recovering? Certainly it can’t be that much of a ranking signal—although they mentioned it would increase in importance over time?

So after waiting for six months, we reverted the change and switched our blog back to the previous/blog subdirectory. It’s still hosted on GitHub Pages and we’re using a simple Nginx proxy to show the content underiwantmyname.com/blog:

location = /blog {
  # GitHub Pages doesn't redirect this properly, so we'll handle it
  return 301 /blog/;
}

# ^~ to allow /blog/ to match before our other regex locations
location ^~ /blog/ {
  proxy_pass https://iwantmyname.github.io;
  proxy_intercept_errors on;
  # serve custom 404 page from our blog repo instead of GitHub Pages' 404
  error_page  404  /blog/404.html;
  # allow GitHub to pass caching headers instead of using our own
  expires off;
}

An important side effect is that our blog pages are now secured under our primary SSL certificate again.

Based on this experience and the following recommendation from Moz’s Rand Fishkin, we decided it would be better for our long-term SEO strategy to put our blog back on our primary domain:

I would still strongly urge folks to keep all content on a single subdomain. We recently were able to test this using a subdomain on Moz itself (when moving our beginner’s guide to SEO from guides.moz.com to the current URLhttp://moz.com/beginners-guide-to-seo). The results were astounding - rankings rose dramatically across the board for every keyword we tracked to the pages.

We will certainly keep a close eye on traffic for the next few months and keep you updated. Hope this helps some of you when deciding on the age-old debate of whether you should have your blog on a subdomain or not!