List of Stack Exchange subdomains that are not mentioned in "All Sites"

Question

I wanted a list of sub-domains of Stack Exchange that are not mentioned over here https://stackexchange.com/sites

Some of the sub-domains I found which were not mentioned are

• Stack Exchange Chat

• Stack Exchange Data Explorer

Are there any other which are not mentioned?

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Mentions by Shadow Wizard, iBug, Glorfindel

• Stack Exchange Development site
• Stack Overflow Blog
• StackPromos
• Stack Overflow Business
• Stack Overflow Insights

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Other mentions below which are not mentioned in "All Sites" but are mentioned in the drop down menu on the top left of the Stack Exchange website

• Area 51
• CS50
• StackApps

Any other website that's left out ?

Answer 1

All sites that are not actual Q/A sites are not listed.

• SE Chat
• SE Data Explorer - Often referred to as SEDE
• SE Dev Test site
• SE OpenID
• A few redirector sites (some of which changed names/domains in the past)
  • Ask Ubuntu (You can refer to AU with [ubuntu.se] as a quick shorthand link in comments)
  • MathOverflow
  • Nothing to Install (later Web Applications)
  • Mi Yodeya
  • Basically Money (later Personal Finance & Money)
  • Fantasy (later Science Fiction & Fantasy)
  • Health (later Medical Sciences)
• Web Socket, the socket that powers the realtime page

Strictly speaking, Area 51 is not in the list, but it's easily known and accessible (it's in the top-left dropdown menu of all sites, though).

Other (sub)domains of Stack Overflow:

• SO Chat
• Stack Overflow Blog
• SO Blog Alternative, redirects to above
• Stack Overflow "Facebook" tag - Redirects to SO with the facebook tag (previously, a truckload of facebook-related tags)
• Stack Overflow Jobs - Discontinued as of April, 2022 (previously redirected to SO Talent)
• Stack Overflow Careers - Discontinued as of April, 2022 (previously redirected to SO Talent)
• Stack Overflow Talent - ↑↑↑
• RADS - Used to be a dedicated redirection site. Closed now (redirects to SO)
• SO Developer Console - Not a test site! Only used by staffs
• DevDays - This has been discontinued.
• SO Email Host
• SO Email Host Alt

• The other Steve

Other apex domains that the Stack Exchange company owns:

• Stack Promos

• SO Business

• StackAuth (The server that enables cross-domain login so you don't have to login separately to SO, SU, SF, AU, etc.)

• Stack Snippets

• Stack Overflow for Teams - since the removal of Teams from the main site domain and sidebar

Answer 2

In addition to the sites mentioned by iBug, we have:

• Area 51 (it's linked to at the bottom of the list, but it's not in the list)
• Stack Exchange API
• The various Winter Bash sites:
  • Winter Bash 2016
  • Older years exist as well, but redirect to stackpromos.com
• CS50 (a Q&A site for Harvard University's CS50x course)
• We used to have elections.stackexchange.com but it's currently down.