# DNS: definition

> DNS (Domain Name System) is the system that translates a domain name into an IP address, so the browser knows which server to contact to display a site.

- Source canonique : [https://allaux.fr/en/glossaire/dns](https://allaux.fr/en/glossaire/dns)
- Langue : EN
- Dernière mise à jour : 2026-09-30

## Why DNS directly concerns an online seller

Every domain name is tied to DNS records: an A record points to an IP address, a CNAME redirects a subdomain to another name, and an MX record indicates which server receives the domain's e-mails. A mistake in these settings is enough to make a shop unreachable or cut off order e-mails, even if the site itself works perfectly.

These settings are changed in the DNS zone, managed at the registrar (where the domain was bought) or at the host. After a change, it doesn't take effect everywhere instantly: DNS propagation can take anywhere from a few minutes to about 48 hours depending on the configured TTL, which explains why a site can look "half-migrated" after a change of host.

## In practice

> When migrating hosts, it's advisable to lower the TTL on records a few days ahead of time, so the switchover propagates faster on the day of the change.

## FAQ

### Why does my site still show the old version after a change of host?

The browser or internet provider keeps the old IP address cached until the TTL expires. Usually, waiting for propagation is enough.

### Does DNS affect the receipt of order e-mails?

Yes, indirectly: if the MX record is misconfigured, transactional e-mails may never arrive, even though the shop otherwise works normally.

### Do you need to touch DNS to install an SSL certificate?

Not always, but some validation methods require adding a temporary TXT record to the DNS zone before the certificate is issued.