Site

The site of a piece of web content is determined by the registrable domain of the host within the origin. This is computed by consulting a Public Suffix List to find the portion of the host which is counted as the public suffix (e.g. com, org or co.uk).

The concept of a site is used in SameSite cookies, as well as a web application's Cross-Origin Resource Policy.

Examples of same site

https://developer.mozilla.org/en-US/docs/
https://support.mozilla.org/en-US/
same site because registrable domain of mozilla.org is the same
http://example.com:8080
https://example.com
same site because scheme and port are not relevant

Examples of different site

https://developer.mozilla.org/en-US/docs/
https://example.com
not same site because registrable domain of the two URLs differs

Specifications

Specification Status Comment
URL Living Standard Initial definition