DNS (Domain Name System) is a system that allows computers from around the world to translate human-readable domain names (such as `yolo.com`) to machine-understandable addresses called IP addresses (such as `11.22.33.44`). For this translation (and other features) to work, you must carefully configure DNS records.
YunoHost allows you to manage and serve several domains on the same server with the same public ip. For instance, you can host a blog and Nextcloud on a first domain `yolo.com`, and a web mail client on a second domain `swag.nohost.me`. Each domain is automatically configured to handle web services, mail services and XMPP services.
In order to make self-hosting as accessible as possible, the YunoHost Project provides a *free* and *automatically configured* domain name service. By using this service, you won't have to [configure DNS records](/dns_config) yourself, which can be tedious and technical.
In more, YunoHost uses an integrated dynamic DNS mechanism, so your server can stay reachable even if your public IP change.
To get one of this domain you simply need to choose `I don't have a domaine name…` during the initial configuration (postinstall) or on the `Add domain` page.
![Here a screenshot of the "Add domain" page where you can choose "I don't have a domain name"](image://webadmin_dyndns.png)
! To limit resources costs and abuses, each instance may only have one of these domains setup at any given time, however you can add as many sub-domains of it as you wish. For example, if you choose `example.noho.st` you can later add the domains `video.example.noho.st` or `www.example.ynh.noho.st` or any other sub-domain you may need. In this case you need to select `I already have a domain name`.
!! You have to keep a backup archive of the config file of your server if you want to be able to restore your server with this domain name without [asking help of YunoHost team to recover access on it](https://forum.yunohost.org/t/nohost-domain-recovery-suppression-de-domaine-en-nohost-me-noho-st-et-ynh-fr/442).
However, you have to pay for it each year (about 15€/year) and you have to do some extra configuration to [setup a correct DNS zone](/dns_config). Our diagnosis tool can trigger alert to help you to do this configuration.
If you already have your own domain, you can simply click "I already have a domain name…". If you don't, in order to simplify and automate the DNS configuration, we suggest you to buy it from a [registrar whose API is supported by YunoHost](/providers/registrar).
Starting from YunoHost v4.3, domains ending by `.local` are fully supported, in addition to the default `yunohost.local`.
They do not use the DNS protocol, but the mDNS one (also known as Zeroconf, Bonjour), which allows them to be published with no specific configuration but exclusively on your local network or VPN.
Their use is this especially suitable when you do not need your apps to be available on the Internet.
![Here a screenshot of the "Add domain" page where you can choose "I already have a domain name" and setup your domain ending by .local](image://webadmin_domain_local.png)
The domain chosen during the initial configuration (post-install) is defined as the main (or default) domain of the server : this is where [the user portal (SSO)](/users) will be available. The main domain can later be changed through the web admin in Domains > (the domain) > Set default, or with the command line `yunohost tools maindomain`.
More technically, the main domain is also used as hostname by SMTP protocol to send email (EHLO) and determine which value should be configured in the reverse DNS bind to your public IP. If this 2 values are mis-configured, the diagnosis tool will trigger you an alert.
If your domain has special, non-latin characters, it will be transformed by YunoHost into its [internationalized version](https://en.wikipedia.org/wiki/Internationalized_domain_name) through [Punycode](https://en.wikipedia.org/wiki/Punycode). So when you use the command line, you have to use the punycode format return for example by `yunohost domain list`.
Another important aspect of domain configuration is the SSL/HTTPS certificate. YunoHost is integrated with Let's Encrypt, so once your server is correctly reachable from anybody on the internet through the domain name, the administrator can request a Let's Encrypt certificate. See the documentation about [certificates](/certificate) for more information.