Know-How Exchange : SEO/SEM

With a space, 'link: www.tauros.eu' is seen by Google as 'link www.tauros.eu' and is not a Google command.

The other two forms you mention are practically the same. There's one situation where they are not the same: if tauros.eu and www.tauros.eu point to different pages or (sub)sites, Google will report separately on them

My understanding is as follows:

Link:https://www.yoursite.com - locates backlinks

Link: yoursite.com - locates occurrences of the text "yoursite.com" and not necessarily locating backlinks

Link:yoursite.com - locates links that should be redirected using a permanent 301 redirect comand to https://www.yoursite.com

Also, user ratings indicate that Google's Link: command is not efficient and that Yahoo's Linkdomain: command is more accurate

This is what I found when I researched your question. Hope it helps.

Here's a link to one thread about Google Link: command:
https://forums.digitalpoint.com/showthread.php?t=108570

Marketing-Riot

Yep, Marketing-Riot is closest to the point.

When you check backlinks and see somesite.com + https://www.somesite.com it means Google is indexing both of these as separate sites.

This is a BIG problem for SEO When two instances of the same site www. and non-www show up in the rankings. Because external links are being divied up between the two, half of those won't count for SEO.

If your site is on an Apache server this is something you can fix via a canonical redirect. Just google it.

It's a good idea to decide how you want your site to be indexed and/or searched. Will you use https://www.yourwebsite.com or https://yourwebsite.com?

I use www because that's most popular and standard in use. So if you decide to use www, then use that in all your backlinking campaigns and in your "link to my site" code. And be sure you use a redirect to your https://www.yourwebsite.com just in case there are links out there that point to https://yourwebsite.com.

Do a backlink search for both. Then determine how many of each you have out there on the web and on what pages they are on and what the Page Rank (PR) is for those pages. Then stick with the strongest from here on out.

This way you will be building strength in Google for only one pointer instead of dividing it.

I usually omit the www when using the link: advanced operator when quickly evaluating a site because it will show a greater number of links by including the https://mysite.com and https://www.mysite.com links and other subddomains. From there I can do a 301 redirect to canonicalize on the preferred URL and consolidate what fragmented links may exist.

Using www will also enable you to segregate your links. For example, www is a subdomain of the top level domain. By utilizing www you can determine the number of links for that subdomain by specifying it in the query (IE: link:www.somewebsite.com). This would be true for other subdomains (IE: link:blog.somewebsite.com).

By omitting the www and specifiying link:somewebsite.com you will receive the aggregate count of the links to both the www and non www versions of the URL.

Here are a couple of my articles on choosing canonical URLs:
https://www.trinitysem.com/2007/06/18/choosing-www-vs-non-www-url/
https://www.trinitysem.com/2007/06/06/canonical-url-www-vs-no/

Google is not transparent when it comes to displaying links however. If you want t a better picture, you'll need to log into your webmaster tools account.

Yahoo! deserves kudos for providing link counts but I'm noticing lately that they are not displaying all results for every query. Therefore, if you do not have Webmaster Tools access, Yahoo may be the better choice.

In Yahoo you would replace the "link:" operator with "linkdomain:".

For either search engine you may wish to add the "-site:" operator to eliminate your internal linking structure from the count and receive a truer picture of who is linking to you.

In this case the query would be:

link:mysite.com -site:mysite.com
in Google

or

linkdomain:mysite.com -site:mysite.com
in Yahoo.