Custom Domain
Definition
Connecting a custom domain is a three-part arrangement, and every hosting platform implements the same three parts under slightly different names. First, a DNS record at your provider sends the name to the host. Second, the host verifies that the name really is yours, usually with a TXT record or by watching for the exact record it asked for. Third, an SSL certificate is issued for the name so the browser does not warn. Only when all three are in place does the host recognise the incoming request as yours and serve your content instead of a stranger's. The order matters more than people expect: the record on its own does nothing if the host has never been told the name exists.
Why It Matters
The visible payoff is trust — a proposal at files.hart.co.uk reads differently from the same file at a platform address, particularly in a procurement inbox. The invisible payoff is bigger. Because the name is yours, moving hosts later is a record change rather than a reprint of every business card, email signature and PDF footer that quotes the link. Search engines treat the two addresses as separate sites, so anything you build under a borrowed address builds it for someone else. And links shared internally tend to outlive contracts: a name you control is still resolvable in five years, while a provider's subdomain is only yours while you are a customer.
How It Works
You add the domain in the host's dashboard first, which makes the host expect it and hands you the exact values to use. For a subdomain you add a CNAME record pointing at the target hostname the host gave you. For the bare name you cannot use a CNAME, so you use whatever the host offers at the apex domain instead: an ALIAS record, CNAME flattening, or an A record aimed at a documented address. You then add any TXT record the host asks for as proof of control, and wait while it checks. Once verification passes, the platform requests a certificate — typically over the ACME protocol, with either an HTTP challenge on a well-known path or a DNS challenge — and starts matching the Host header on incoming requests to your site.
Real-World Example
On 99helpers a published file is live at your-name.99helpers.site for nothing, and that address will carry on working. A paid plan lets you put your own name in front of it, so the same 4 MB pitch deck answers at pitch.acme.com with its version history, password protection and analytics untouched. The change is one CNAME at the registrar plus a verification record, and the certificate is issued without being asked for. Visitors who bookmarked the old address are redirected rather than stranded.
Common Mistakes
- ✕Pointing the domain before adding it in the host's dashboard — the host has no mapping for that Host header and answers with a 404 or someone else's site
- ✕Leaving the previous A record in place beside the new record — resolvers hand out either one, so the site works for some visitors and not others
- ✕Using the registrar's forwarding or parking service instead of a real record — the content ends up inside a frame, the address bar never changes and the certificate never issues
Related Terms
Apex Domain
The apex domain is the bare name with nothing in front of it — acme.com rather than www.acme.com. It is also called the root domain, the naked domain or the zone apex.
CNAME Record
A CNAME record points one name at another name rather than at an address. Hosts ask for them because the addresses behind their target hostname can then change without you touching your zone.
TXT Record
A TXT record holds plain text at a DNS name. For anyone hosting files or a site, the reason you meet one is domain verification — proving to a provider that the name really is yours.
SSL Certificate
A small signed file that proves a server is genuinely the one answering for a given hostname, so a browser will open an encrypted connection to it. Everyone calls it an SSL certificate, though the protocol it is used with has been called TLS for years.
Public URL
An address that serves its content to anyone who requests it, with no sign-in, token or password. Having the address is the only requirement.
Put a file online in seconds
Drop in a document, an image, a page or a whole static website and share the link — free, with no build step and no server to set up.
Host a file free →