As the title states, why does Stack Exchange (SE) have Stack Overflow (SO) its' own domain, and yet everything else is just sub-domains under SE?

Is it because SO came first, and then SE was a product of that?

Just curious...

  • 1
    Not only Stack Overflow, SOFU
    – Arulkumar
    Commented Jun 6, 2017 at 17:14
  • "Everything else" is not the case. The three "trilogy" sites are all custom URLs... so SO, SF, SU. There are also several other sites that have custom URLs but automatically convert to the XXX.SE format (seasonedadvice.com or arqade.com).
    – Catija
    Commented Jun 6, 2017 at 17:14

1 Answer 1


Stack Overflow isn't the only site with its own domain.
All the members of the trilogy have their own domains:

The trilogy were the first three Stack Exchange sites. You can find more information on the blog:

Custom domains was something tried for the later sites. It was given up and any custom domains created were redirected to the subdomain (e.g. askdifferent.com). You can find the full explanation for the reversal on the blog:

There are still other sites which use custom domains:

  • So I guess a better question would be, why does SE not have these other sites (like trilogy) under sub domains too? Why not redirect like the others you mentioned?
    – hack3rfx
    Commented Jun 6, 2017 at 17:26

Not the answer you're looking for? Browse other questions tagged .