[seo] Can a relative sitemap url be used in a robots.txt?

In robots.txt can I write the following relative URL for the sitemap file?

sitemap: /sitemap.ashx

Or do I have to use the complete (absolute) URL for the sitemap file, like:

sitemap: http://subdomain.domain.com/sitemap.ashx

Why I wonder:

• I own a new blog service, www.domain.com, that allow users to blog on accountname.domain.com.
• I use wildcards, so all subdomains (accounts) point to: "blog.domain.com".

In blog.domain.com I put the robots.txt to let search engines find the sitemap. But, due to the wildcards, all user account share the same robots.txt file.Thats why I can't use the second alternative. And for now I can't use url rewrite for txt files. (I guess that later versions of IIS can handle this?)

Google crawlers are not smart enough, they can't crawl relative URLs, that's why it's always recommended to use absolute URL's for better crawlability and indexability.

Therefore, you can not use this variation

> sitemap: /sitemap.xml

Recommended syntax is

Sitemap: https://www.yourdomain.com/sitemap.xml

Note:

• Don't forgot to capitalise the first letter in "sitemap"
• Don't forgot to put space after "Sitemap:"

Good technical & logical question my dear friend. No in robots.txt file you can't go with relative URL of the sitemap; you need to go with the complete URL of the sitemap.

It's better to go with "sitemap: https://www.example.com/sitemap_index.xml"

In the above URL after the colon gives space. I also like to support Deepak.