get-apex-domain
v1.1.0
Published
Returns the apex domain (aka base, bare, naked, root apex, or zone apex domain) of the current web page without the use of a public suffix list. The apex domain is also the top-most domain that allows for setting cookies.
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get-apex-domain
Returns the apex domain (aka base, bare, naked, root apex, or zone apex domain) of the current web page without the use of a public suffix list. The apex domain is also the top-most domain that allows for setting cookies.
Because of the methodology used, this library is very small.
What's an apex domain?
An apex domain is the longest portion of a domain that does not contain a subdomain. In the case of store.example.co.uk
, example.co.uk
would be the apex domain.
When a website owner attempts to register a domain name, they cannot register a domain matching an effective top-level domain (e.g., com
, co.uk
) due to restrictions controlled by registrars. However, domains ending in an effective top-level domain are allowed (e.g., example.com
, example.co.uk
). This is the apex domain. The domain name owner can then create subdomains ending in the domain they registered (e.g., store.example.com
, store.example.co.uk
), but subdomains are not apex domains.
Requirements
This will only work in a browser and cookies must be enabled.
How detection is accomplished
As it turns out, browsers allow websites to set cookies for apex domains (e.g., example.co.uk
) but not top-level domains (e.g., uk
) or effective top-level domains (e.g., co.uk
).
Considering a hostname of store.example.co.uk
, we can determine the apex domain by attempting to write a cookie on uk
, then co.uk
, then example.co.uk
, then store.example.co.uk
, until we succeed in writing a cookie. In this case, the first attempt that will succeed is example.co.uk
. This is the apex domain.
Installation
If you use npm for package management, you can install get-etld
by running the following command from within your project's directory:
npm install get-apex-domain
Usage
import getApexDomain from "get-apex-domain";
console.log(getApexDomain());
If cookies are not enabled, an error will be thrown.
The localhost
hostname presents a unique case. If the hostname is localhost
, the returned apex domain will be undefined
.
Special Recognition
Full credit goes to Joe Khoury for devising the strategy used to determine the apex domain.