HTTPS-records allows browsers to efficiently obtain complete instructions for accessing a web-site for a domain name - including supported protocols (HTTP/1.1, 2, 3, etc.), ip address(es), port number, and public keys (all optional) - saving the browser from doing a number of DNS lookups and other protocol negotiation steps.
An HTTPS-record provides instructions for accessing a web-site with the following properties:
Mode
Choose between: Service, Alias, or Service not available / does not exist.
In "Alias" mode, the HTTPS-record functions similar to a CNAME-record - execept only for HTTPS-record requests - which means that it can also appear a the zone name level (unlike CNAME).Priority
The order of priority (1-65535) - if multiple HTTPS records are available for the same name.Service host name
The host name of the web-server.Protocol identifiers (ALPN IDs)
The ALPN (Application Layer Protocol Negotiation) IDs of the protocols supported by the web-server.
The default is "http/1.1" - meaning HTTP version 1.1.
See the official list of ALPN IDs at https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#alpn-protocol-ids
For example, "h2" means HTTP v. 2 and "h3" means HTTP v. 3. Identifiers in the format "h3-[draft]" like "h3-27" have also been observed "in the wild".IP address(es) (optional)
The IP addresses (IPv4 and/or IPv6) of the server(s) hosting the web-site.
This is considered a hint only - a client may choose to resolve the host name property instead of using this.Port number (optional)
An alternate port number for the web-server (other than 443).Encrypted ClientHello (ECH) (optional)
ECH configuration (ECHConfigList) for the web-server encoded in Base64 format.
To create a new HTTPS-record, right-click a zone in the left list in the DNS Records window, and select "Other new record" from the pop-up menu.
This record type is defined in https://datatracker.ietf.org/doc/draft-ietf-dnsop-svcb-https (Not yet an official RFC at the time of this writing, but expected to be so soon)