Why doesn't google look at identical url paths on https, http, www, and no-www variants of the url, and if they look similar then use some default google policy to select which of them is canonical?
It's not safe to merge www.domain1.com and www.domain2.com. it's not safe to merge subdomain.domain.com and www.domain.com. However, for the limited cases of www and no-www, https and http, if they look similar, I think it's harmful not to treat them as the same site. You can't expect every website owner to be aware of this issue.
If it's a matter of not being able to be 100% sure, is there a single site that cares about google ranking that runs different sites on different combinations of www/no-www and https/http, but has similar content that would confuse a simple heuristic looking at page similarity? In what sort of circumstance could that happen other than with placeholder pages?
GWT allows selecting a preference between www and no-www, but I don't see a preference between https and http. I think Google should add a notice that using GWT to select between www and no-www is deprecated and the recommended way to handle www, no-www, http, and https selection is to use 301 redirects or rel="canonical" tags.
Comments
Why doesn't google look at identical url paths on https, http, www, and no-www variants of the url, and if they look similar then use some default google policy to select which of them is canonical?
For example, if http://mydomain.com/path and https://www.mydomain.com/path have 95% content correlation and repeated requests to http://mydomain.com/path have 95% content correlation, and the server headers look the same, why would it not be safe to decide those are duplicates of a single canonical url?
It's not safe to merge www.domain1.com and www.domain2.com. it's not safe to merge subdomain.domain.com and www.domain.com. However, for the limited cases of www and no-www, https and http, if they look similar, I think it's harmful not to treat them as the same site. You can't expect every website owner to be aware of this issue.
If it's a matter of not being able to be 100% sure, is there a single site that cares about google ranking that runs different sites on different combinations of www/no-www and https/http, but has similar content that would confuse a simple heuristic looking at page similarity? In what sort of circumstance could that happen other than with placeholder pages?
GWT allows selecting a preference between www and no-www, but I don't see a preference between https and http. I think Google should add a notice that using GWT to select between www and no-www is deprecated and the recommended way to handle www, no-www, http, and https selection is to use 301 redirects or rel="canonical" tags.