What is the current "standard" practice for mobile (m.*) domains (and why)? When should I use them? When should I not?

I've read some sources online (mainly stackoverflow and the google developer docs), but wondered if someone could shed some more light on this. I've also noticed that stackexchange sites don't seem to redirect to a mobile-only domain when the "desktop" link is opened on a mobile device. But reddit, for example, does redirect to a mobile domain. Try clicking on these two links from a smartphone, for example:

My instinct would be to say that the stackexchange behavior is more webby, because it treats the URL as canonical and hides the User-Agent sniffing from the client*. If the user shares the URL with a friend, the friend doesn't know if she accessed the content originally from a mobile or desktop device. And that's a Good Thing (tm).

But I would like to know if there are any practical or historical reasons for using mobile domains vs. (what I'm calling here) canonical URLs.

* I actually didn't check if stackexchange really does agent sniffing, but you get the idea...

  • 1
    This is unfortunately too broad and opinion-based to answer here conclusively. As you noted, mobile subdomains are still being used, particularly by sites that started off using them, since they're structured and indexed that way. Newer sites tend to go the responsive direction for ease of design and maintenance... The in's and out's of these are the subjects of lengthy discussions, which doesn't fit well with the format of this site.
    – dan
    Aug 23 '16 at 0:16
  • point taken, @dan. Aug 23 '16 at 0:39

The best practice is making your website responsive, where it alter the content shown using css file/files.

Having a m. subdomain do a serious hit on your domain authority. Having all in one singe domain make all backlinks etc count toward your website for all devices. Plus you only have one page to maintain.

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