An A record is the entry in a domain’s DNS settings that points a name, such as example.co.uk or www.example.co.uk, to the IPv4 address of the server that hosts it. When someone types your address, the A record is what tells their browser which machine to ask for the page.
How an A record works
Every domain has a zone file in the domain name system: a list of records saying where its website, email and other services live. An A record in that list has four parts:
- Host or name. “@” usually means the root domain; “www” means the www subdomain.
- Type. A, for address.
- Value. An IPv4 address, four numbers separated by dots, such as 203.0.113.10.
- TTL. How long, in seconds, other systems may cache the answer before asking again.
An AAAA record does the same job for the newer IPv6 addresses. A CNAME record is different: it points a name at another name rather than at an address, which suits subdomains on hosted platforms. The root domain cannot normally hold a CNAME, which is why platforms such as Shopify and Squarespace give you an A record to add for the root and a CNAME for www.
The records only count where your nameservers point. If your domain is registered with one company but its nameservers point to your host or to Cloudflare, it is the zone at that second company that the world reads. Editing the copy at the registrar changes nothing.
Why it matters
Most of the time you never think about A records. They matter at three moments: launching a site, moving hosting and changing platform. Get them wrong and the site goes offline, or worse, half your visitors see the new site and half the old one. That split is confusing for customers and for Google, especially during a redesign where URLs have changed too.
They also cause collateral damage. Moving nameservers to a new host without copying across the MX records and TXT records is one of the commonest ways small UK businesses lose their email for a day during a website launch.
Common mistakes
- Editing records in the wrong place At the registrar when the nameservers point somewhere else.
- Forgetting www. The root domain moves to the new server, while www still points at the old one.
- Two A records left in place Old and new, so traffic is split between servers.
- A long TTL during a move So the old address stays cached for a day or more.
- Switching off the old server too early Before every resolver has picked up the change.
How to act on it
Before any change, work out where your DNS is actually managed by looking up the nameservers, then export or screenshot the full zone so you can restore it. A day or two before a planned move, lower the TTL on the records you will change to a few minutes. Make the change, then check it with a DNS lookup tool that queries from several locations, and keep the old server running until traffic to it has stopped.
Once the move is settled, raise the TTL again and confirm email, Search Console verification and any third-party services still work. DNS changes are a standard step in a hosting or platform move, and I check them as part of website migration SEO.