zulip/docs/prod-requirements.md

Requirements for Zulip in production

• Server running Ubuntu 14.04 Trusty
• At least 2 CPUs for production use with 100+ users
• At least 4GB of RAM for production use with 100+ users. We strongly recommend against installing with less than 2GB of RAM, as you will likely experience OOM issues. In the future we expect Zulip's RAM requirements to decrease to support smaller installations (see https://github.com/zulip/zulip/issues/32).
• At least 10GB of free disk for production use (more may be required if you intend to store uploaded files locally rather than in S3 and your team uses that feature extensively)
• Outgoing HTTP(S) access to the public Internet.
• SSL Certificate for the host you're putting this on (e.g. zulip.example.com). The installation instructions contain documentation for how to get an SSL certificate for free using LetsEncrypt.
• Email credentials Zulip can use to send outgoing emails to users (e.g. email address confirmation emails during the signup process, missed message notifications, password reminders if you're not using SSO, etc.).

Note that if you just want to play around with Zulip and see what it looks like, it is easier to install it in a development environment following these instructions, since then you don't need to worry about setting up SSL certificates and an authentication mechanism. Or, you can check out the developers' chatroom (a public, running Zulip instance).

For more details, see full instructions for installing Zulip in production.