Two ways to prove you control a domain.
HTTP VALIDATION
The authority asks you to place a file at a specific path. It retrieves the file over HTTP to confirm control.
This is what AutoSSL uses. It requires the domain to resolve to the server and the path to be reachable.
DNS VALIDATION
The authority asks you to add a TXT record with a specific value. It queries DNS to confirm.
This is required for wildcard certificates, and useful when the site is not yet live or is behind a proxy.
WHEN DNS VALIDATION HELPS
Issuing a certificate before pointing the domain at the server Wildcards, which cannot use HTTP validation Sites behind a proxy that interferes with the HTTP path
THE TRADE-OFF
DNS validation requires access to your DNS and, for renewals, updating the record each time unless automated. HTTP validation is fully automatic with AutoSSL.
WHICH YOU WILL USE
Almost certainly HTTP, via AutoSSL, without thinking about it. DNS validation matters only for wildcards and unusual situations.
