Informally, asite is a website, which is a collection of web pages, served from the same domain and maintained by a single organization, defined by itsregistrable domain.

Browsers sometimes need to distinguish precisely between different sites. For example, the browser must only sendSameSite cookies to the same site that set them.

For this more precise definition a site is determined by theregistrable domain portion of the domain name. The registrable domain consists of an entry in thePublic Suffix List plus the portion of the domain name just before it. This means that, for example,theguardian.co.uk,sussex.ac.uk, andbookshop.org are all registrable domains.

According to this definition,support.mozilla.org anddeveloper.mozilla.org are part of the same site, becausemozilla.org is a registrable domain.

In some contexts, the scheme is also considered when differentiating sites. This would makehttp://vpl.ca andhttps://vpl.ca different sites. Including the scheme prevents an insecure (HTTP) site from being treated as the same site as a secure (HTTPS) site. A definition that considers the scheme is sometimes called aschemeful same-site. This stricter definition is applied in the rules for handlingSameSite cookies.

Examples

These are the same site because the registrable domain ofmozilla.org is the same:

• https://developer.mozilla.org/en-US/docs/
• https://support.mozilla.org/en-US/

These are considered the same site because the port number is ignored when determining the site:

• https://example.com:8080
• https://example.com

These are not the same site because the registrable domain of the two URLs differs:

• https://developer.mozilla.org/en-US/docs/
• https://example.com

These are the same site, or different sites if the scheme is considered:

• http://example.com
• https://example.com

See also

• What is a URL
• Related glossary terms:
  • Origin
  • Registrable domain
• Same-origin policy