How/why did non-www version of page on my site get indexed?

Question

For some reason there are 3 or 4 pages on my site for which Google has indexed the non-www version.

I 301 redirect all requests to https and www in .htaccess but it's very odd to me that when I search for My Company Name demo that the only result for the corresponding page on my site does not have the www (https://my-company-name.com/request-demo). However if I search for My Company Name free trial, the result for the corresponding page does include the www (https://www.my-company-name.com/free-trial). The pages are almost identical in code... in fact the free trial page was created by cloning the demo page in WordPress.

Now that I have the redirect to www in place, this is no longer problematic, but for the sake of consistency, curiosity and avoiding introducing potential problems down the line (for SEO, will the www version of this page be considered "duplicate content"?), I'd love to "un-index" the non-www version and have the search results show (and link to) the www version.

Any ideas on how i can go about achieving this? And perhaps more importantly, does anyone have an explanation as to why/how this is happening?

Answer 1

If there are any links to the non-www version of the URL from anywhere then it can result in the non-canonical URL being indexed.

Also check that you have:

• the correct rel="canonical" link element in your pages (and/or Link HTTP response header).

• the correct URL stated in your XML sitemaps, RSS feeds, etc.

• the correct preference set in Google Search Console: www vs non-www

Now that I have the redirect to www in place, this is no longer problematic

Although you do still need to make sure you have no internal links to the non-canonical URL.

Answer 2

MrWhite has given a good answer about why this might be happening, but I just wanted to address the other part you mentioned:

...and avoiding introducing potential problems down the line (for SEO, will the www version of this page be considered "duplicate content"?), I'd love to "un-index" the non-www version and have the search results show (and link to) the www version.

If both the www and non-www pages are indexed then yes - Google would consider this duplicate content.

However if the 301 redirect is set up properly, then Google will eventually pick up this redirect and change the listing in the SERPs instead of indexing both.

It can take some time for it to pick it up automatically so I suggest submitting the www page for reindexing using Google Search Console.

You could also use Google Search Console to request that the non-www page is removed from the listings - it might be a drastic action, but if you are worried about duplicate content or that the redirect might not be working correctly, it might be worth considering after you take the steps MrWhite outlined in his answer.