Mobile SEO… Man, can it be complicated. Especially mobile SEO for a subdomain when you are working with a massive website and you need to map everything together, account for rouge URLs and just generally get it done. I have been doing a lot of this lately, so I wanted to share 2 devastating mobile subdomain SEO concepts (none that I made, but am happy I noticed) that you need to be aware of. Oh, and by the way, this all comes from Google documentation. I didn’t make this stuff up.
One of the most important things you need to do in a mobile subdomain configuration is map the mobile domain to the desktop with rel=”canonical” and rel=”alternate”. But, what a lot of people forget is that you need to keep a 1 to 1 ratio. So you cannot map a bunch of desktop URLs to one mobile URL or you will have some major issues.
According to Google, “When using rel=”alternate” and rel=”canonical” markup, maintain a 1-to-1 ratio between the mobile page and the corresponding desktop page. In particular, avoid annotating many desktop pages referring to a single mobile page (or vice versa).”
If you get this wrong, and map too many URLs to one place, Google may not show them in search.
Have Correct Redirects
Just like the mapping situation, you need to make sure your redirects are in line. According to Google you need to, “Make sure that desktop pages don’t inadvertently redirect to a single, unrelated mobile page. HTTP redirection is a commonly used to redirect clients to device-specific URLs. Usually, the redirection is done based on the user-agent in the HTTP request headers. It is important to keep the redirection consistent with the alternate URL specified in the page’s link rel=”alternate” tag or in the Sitemap.”
So if you have a rel=”canonical” and a rel=”alternate” map, and also have redirects in place to ensure the user ends up on the right URL based on their device, you need to be sure that they are being redirected to the mapped URL. Google goes on to say that they actually prefer a 302 redirect in this situation.
“For this purpose, it does not matter if the server redirects with an HTTP 301 or a 302 status code, but use of 302 is recommended whenever possible.”
Google does not care if you redirect mobile users to desktop or viseverse
“For Googlebot, we do not have any preference and recommend that webmasters consider their users when deciding on their redirection policy. The most important thing is to serve correct and consistent redirects, i.e. redirect to the equivalent content on the desktop or mobile site. If your configuration is wrong, some users may not be able to see your content at all.”
Did you catch that! So if you have the wrong configuration here, some users might not be able to see your content at all. So many sure that you get it right.
Google has one last suggestion in this area.
“We suggest giving users a way to override the redirect policy, i.e. allowing mobile users to view the desktop page and allowing desktop users to see the mobile page if they so choose.”
This is a good idea. I often end up on a desktop site on my mobile phone and then click to desktop. It is a nice open.
These two mobile subdomain configuration rules are very important and could cost you big if you mess them up. Make sure that you map your mobile and desktop site correctly with alternate and canonical. In addition, be sure your redirects match your configuration.