Setting a preferred domain in Google webmaster tools

Question

I have a site like "example.com".

Questions 1: I can access to my site through "example.com" and www.example.com in web browser. Both non www and www version redirects to example.com. So, is it necessary to add my both version of domain in webmaster tool or I should only add non www version site in webmaster as I can access to my website through www/non www version.

Question 2: When/why do I need to set preferred domain in webmaster tools.

Questions 3: Is it necessary to set 301 redirect, if I set my preferred domain name in webmaster tool.

As I am a non technical guy, I need your valuable feedback to improve my knowledge.

Answer 1

1) Correct. You only really need to add the non-www version. Google treats www and non-www as separate websites. Same goes for http or https (if that is a factor for you). https://support.google.com/webmasters/answer/34592?hl=en

2) See the article above for why you'd need a separate website. The main reason, from that article, is that "Search Console data and reporting work best on a site level." So, www.example.com and example.com are treated differently. That said, you may want to add both so you can see data for both. However, if you are only using non-www, then that is the one you'll care the most about getting data for.

3) Yes, if you are using non-www as the canonical version of your domain, you want to have the www version redirect with a 301 status response code. The verification in Google Search Console is helpful, but not a definitive statement that everybody can see (i.e. Google can see your verified domain, but Bing can't). By putting in the 301 redirect from www to non-www, you are telling the web that you permanently, definitively want the non-www version to be the official/canonical version of your domain.

Answer 2

For Q1: Provided your redirect from www.example.com to example.com forces all requests to be redirected and doesn't just apply to your root folder for example, then you will not need to add www.example.com to your Webmaster Tools as a property.

For Q2: This feature of Webmaster Tools is more helpful for setting a preference between SSL and non-SSL versions of your site as it would treat these as separate properties.

For Q3: Setting the preferred domain in Webmaster Tools will not affect the behaviour of your website, but only how it is indexed in Google. For your website to behave consistently and be effective with SEO strategies you will need to ensure www.example.com redirects to example.com with a 301 redirect header (or vice versa if you choose to prefer the www version).