Public Suffix List
A community-maintained list of domain suffixes under which anyone can register names, such as com, co.uk or github.io, used to find where a registrable domain begins.
What it means
Domain names do not reveal where public registration ends and a private domain begins: example.co.uk is registrable, co.uk is not. The Public Suffix List, maintained by Mozilla volunteers with submissions from registries and published at publicsuffix.org, records those boundaries for browsers, cookie rules and other software.
DMARC under RFC 7489 used it to determine organizational domains, though the RFC did not mandate any particular list or update schedule, which allowed receivers to disagree. RFC 9989 replaced that use with the DNS tree walk. The list still matters to receivers running older implementations and to other tools.
Its private section includes hosting platforms, so a subdomain of such a platform counts as its own organization.
Related terms
Sources
What this definition rests on. The wording is ours; the facts are theirs.
- Public Suffix Listpublicsuffix.org
- Public Suffix List: Learn morepublicsuffix.org
- Public Suffix List: the list file (ICANN and private sections)publicsuffix.org
- RFC 9989: Domain-based Message Authentication, Reporting, and Conformance (DMARC), section 4.10rfc-editor.org
- RFC 9499: DNS Terminology, section 9rfc-editor.org
All 432 terms in the glossaryThe wiki: blocklists and bounce codes