# Hosting multiple organizations

The vast majority of Zulip servers host just a single organization.
This article documents what's involved in hosting multiple Zulip
organizations on a single server.

Throughout this article, we'll assume you're working on a zulip server
with hostname `zulip.example.com`.

## Subdomains

Zulip's approach for supporting multiple organizations on a single
Zulip server is for each organization to be hosted on its own
subdomain.  E.g. you'd have `org1.zulip.example.com` and
`org2.zulip.example.com`.

Web security standards mean that one subdomain per organization is
required to support a use logging into multiple organizations on a
server at the same time.

When you want to create a new organization, you need to do a few
things:

* If you're using Zulip older than 1.7, you'll need to set
  `REALMS_HAVE_SUBDOMAINS=True` in your `/etc/zulip/settings.py`
  file.  That setting is the default in 1.7 and later.
* Make sure you have SSL certificates for all of the subdomains you're
  going to use.  If you're using
  [our LetsEncrypt instructions](ssl-certificates.html), it's easy to
  just specify multiple subdomains in your certificate request.
* If necessary, modify your `nginx` configuration to use your new
  certificates.
* Use `./manage.py generate_realm_creation_link` again to create your
  new organization.  Review
  [the install instructions](prod-install.html) if you need a
  refresher on how this works.

For servers hosting a large number of organizations, like
[zulipchat.com](https://zulipchat.com), one can set
`ROOT_DOMAIN_LANDING_PAGE = True` in `/etc/zulip/settings.py` so that
the homepage for the server is a copy of the Zulip homepage.

### The root domain

Most Zulip servers host a single Zulip organization on the root domain
(i.e. `zulip.example.com`).  The way this is implemented internally
involves the organization having the empty string (`''`) as its
"subdomain".  You can mix having an organization on the root domain
and some others on subdomains (e.g. `it.zulip.example.com`).