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

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
same site because registrable domain of is the same
same site because scheme and port are not relevant

Examples of different site
not same site because registrable domain of the two URLs differs


Specification Status Comment
URL Living Standard Initial definition