Domain aliasing
Mapping one domain to another so requests for the alias are served by the target. Implemented at DNS (CNAME), HTTP (redirect), or routing layer (transparent proxy).
Domain aliasing is the umbrella term for "this domain is another name for that domain." Three implementations sit under it.
The three flavors
DNS aliasing (CNAME). A DNS record says alias.com is a canonical name for target.com. Resolvers follow the CNAME chain. End-user sees alias.com in their browser the whole time. See CNAME record.
HTTP aliasing (redirect). A 301 or 302 response from the server tells the browser to go to a different URL. The address bar changes. See Domain forwarding.
Routing-layer aliasing (transparent proxy). Your edge accepts alias.com, fetches from target.com internally, returns the response as if it came from alias.com. The browser never sees target.com. This is what domain mapping does in SaaS custom-domain setups.
Which one to use when
- DNS aliasing: when both domains should resolve to the same IPs and serve the same content.
- HTTP redirect: when you want users to clearly land on the new URL.
- Transparent proxy: when you want the user-facing URL to stay branded but the content lives elsewhere. This is the SaaS custom-domain pattern.
The terms get conflated in marketing copy, but the implementation differences matter operationally.