View Full Version : SEO pros/cons of sub-domains

23rd June 2004, 03:27 PM

I have been trying to gather information about using sub-domains. I am under the implression that using sub-domains has a very positive SEO attribute:

**Search engines and directories consider each sub-domain to be a seperate site. So, for instance, one can submit each of their sub-domains to a directory and get them listed in the various categories that are most appropriate for each product offering (this would of course assume that all content is unique in each sub-domain).


Is this a valid SEO strategy?

steve sardell
23rd June 2004, 03:36 PM
Is this a valid SEO strategy?

By valid if you mean allowed, yes it is. Simply take a look at IBM. Is it necessary? IMHO, no. It requires a great deal of work, and for a small company I believe the time can be spent in better directions. It is not a strategy I would rec for anyone but a well seasoned SEO.

David Wallace
23rd June 2004, 03:50 PM
I might add that as far as directories go, you are dealing with the human element and they will rarely if ever list a sub domain URL because they will easily see that the main domain is already listed.

23rd June 2004, 06:33 PM
If your going to crosslink go for the unique IP and domain name for each site.

Old Welsh Guy
24th June 2004, 03:38 AM
Hi TD Ann,

Personally I don't use sub domains at all for SEO reasons, only for practicality or usability. As has been pointed out the bulk of directories are human edited, and while they 'might' get through in different sections, there is a possibility that your competitors will report the fact, and the site gets reviewed, worse case scenario is that you get pulled under every instance, as lets be blunt, you ARE doing it purely for SEO reasons rather than a usability, or any other bona fide reason. That said, it is only a possibility that you could fall foul.

Also to be considered with Google is the fact that Page Rank flows better across a domain than it does across the web, so in fact any gains you get from splitting the site might well be lost in the dampening factor that is applied.

Thirdly As search is moving on, the use of 'word understanding' semantic technology is likely to get incorporated more and more, to give the search engines a better understanding of what a page, site, and relation between pages and sites is all about. Having 100 pages of good quality information is going to tell the SE's what your site is really about, and it is also going to encourage opportunity to secure good quality deep links. This PR will flow around the site freely, and might, end up being of more benefit than splitting the site into numerous sub domains.

Google certainly is going down the rout of Semantics, having bought Applied Semantics, and played with it during the Florida update of late 2003 (dear me I sound like an old timer gold prospector from way back when) Teoma uses clustering, and Google have also said that they use clustering using a 'hub' (a place that links out to many other related sites) and 'Authority' (a place where many related sites link into) system. This clusters sites around themed topics, and links from hubs, and authority sites are deemed to be more relevant than other links for on topic searches. If you split your site into pieces, then you run the risk of an authority link from one, not counting toward the rest of the pages on the other sub domains. Also, if you work on your site, build a resource, research your field, then 'your' site, could eventually become a hub, authority, or even both as is the case with many sites who link out, and have many links pointing back to them.

Hub & Authority sites are relative to the field where they operate in. If there are only 3 sites on the web about your subject (example) and you link to the other two, ant the other two both link to you, but not to each other, then YOUR site links to every other known page about your subject, and every other known page links to you, but every other known page does not link to each other, so that makes you both a hub, and an authority on your chosen subject.

Phew, I have gone off topic a little here (sorry) thatís how I am, get me talking and I can't shut up :p Hope that has helped though


24th June 2004, 09:35 AM

That was a really good read. Thanks.


25th June 2004, 01:13 PM
I think Google does recognize sub domains and does add some value to them:

As you can see it at least recognizes that IBM has used the correct keyword PC within the sub domain. Of course the value in the overall recipe for Google success is very small as mentioned above. Sub directories might as well be used if you are looking to organize a site by using keywords in the URL string.

25th June 2004, 01:16 PM
Welcome to the forum, incrediblehelp! :)

28th June 2004, 12:52 PM
"I might add that as far as directories go, you are dealing with the human element and they will rarely if ever list a sub domain URL because they will easily see that the main domain is already listed."

It depends on how and why the subdomains are being used. There are legitimate reasons to setup a site with subdomains and yes, they could potentially have some impact on SEO, but realistically, I don't view them as having much more of an impact than (since they are essentially the same thing, just displayed a different way.

Consider They use subdomains for all of their sites...

This can be good in that the domains are shorter, easier to remember and have keywords in it, but really, that's more general marketing advantages than something that's going to get you a boost in the rankings.

My thinking with subdomains is to use them if the content of the subdomain "could" legitimately be a seperate site, but makes sense to include as part of a larger site. can easily stand alone as its own site, but it's part of the about network, so it makes sense to format it as a subdomain.

Hope all that made sense...

29th June 2004, 02:07 PM
I agree for the most part Jenn. Subdirectories and sub domains are pretty much the same, but like you mentioned if you website changes look or feel for different categories I would use sub domains, but if the same cosmetic feel is existent for all categories then subdirectories are best.

30th June 2004, 05:21 PM
You don't have to even appear to be seperate sites to get different pages into a directory.

I have got individual pages listed a few times.

For example:

Both were listed, while my main page ( actually hasn't made it yet.

10th July 2004, 10:26 AM
I might add that as far as directories go, you are dealing with the human element and they will rarely if ever list a sub domain URL because they will easily see that the main domain is already listed.

One of the very first sites I submitted to the DMOZ directory was a subdomain site and it was listed in record time - could be one of those rarely times and I was very lucky I guess.

I have submitted other sies with their own url who are yet to be listed