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

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- [SE Chat](https://chat.stackexchange.com)
- [SE Data Explorer](https://data.stackexchange.com) - Often referred to as [SEDE](/search?q=SEDE)
- [SE Dev Test site](https://dev.stackexchange.com)
- [SE **OpenID**](https://openid.stackexchange.com)
- A few redirector sites
  - [Ask Ubuntu](https://ubuntu.stackexchange.com) (You can refer to AU with `[ubuntu.se]` as a quick shorthand link in comments)
  - [MathOverflow](https://mathoverflow.stackexchange.com)
  - [Nothing to Install (later Web Applications)](http://nothingtoinstall.com/)
  - [Mi Yodeya](http://mi.yodeya.com)
  - [Basically Money (later Personal Finance & Money)](http://basicallymoney.com/)
  - [Fantasy (later Science Fiction & Fantasy)](https://fantasy.stackexchange.com)
  - [Health (later Medical Sciences](https://health.stackexchange.com)
- [Web Socket](https://qa.socket.stackexchange.com), the socket that powers [the realtime page](https://stackexchange.com/questions?tab=realtime)

Strictly speaking, [Area 51](https://area51.stackexchange.com) 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](https://chat.stackoverflow.com)
- [Stack Overflow Blog](https://stackoverflow.blog)
- [SO Blog Alternative](https://blog.stackoverflow.com), redirects to above
- [Stack Overflow "Facebook" tag](http://facebook.stackoverflow.com) - Redirects to SO with **a truckload** of [tag:facebook] tags)
- [Stack Overflow Jobs](https://jobs.stackoverflow.com) - Redirects to SO Talent
- [Stack Overflow Careers](https://careers.stackoverflow.com) - Redirects to SO Talent
- [Stack Overflow Talent](https://talent.stackoverflow.com) - ↑↑↑
- [RADS](https://rads.stackoverflow.com) - Used to be a dedicated redirection site. Closed now (redirects to SO)
- [SO Developer Console](https://dev.stackoverflow.com) - Not a test site! Only used by staffs
- DevDays - This has been [discontinued](https://meta.stackoverflow.com/a/265263).
- [SO Email Host](https://email.stackoverflow.com/)
- [SO Email Host Alt](https://stackoverflow.email/)

<!-- This one is suggested by [*Shadow Wizard*](/u/152859) -->

- [The other Steve](https://clc.stackoverflow.com)

### Other apex domains that the Stack Exchange company owns:

- [Stack Promos](https://stackpromos.com)
- [SO Business](https://www.stackoverflowbusiness.com)
- [StackAuth](https://stackauth.com) (The server that enables cross-domain login so you don't have to login separately to SO, SU, SF, AU, etc.)
- [Stack Snippets](https://stacksnippets.net)