Domains · Website glossary

Public suffix

Quick answer · What is Public suffix?

A suffix under which users can register names, including some multi-label and platform-specific boundaries.

IN PRACTICE

Public suffix: an example

A browser may use a public-suffix list when deciding which sites should be treated as separate cookie boundaries.

KEEP IN MIND

A public suffix is not always a single top-level label; simplistic last-two-label rules can be wrong.

Put the idea to work

Frequently asked questions

What is a practical example of Public suffix?

A browser may use a public-suffix list when deciding which sites should be treated as separate cookie boundaries.

Can I identify every registrable domain from its last two labels?

A public suffix is not always a single top-level label; simplistic last-two-label rules can be wrong.

Which concepts should I read alongside Public suffix?

Second-level domain: A domain label immediately beneath a top-level domain in the DNS hierarchy.
Cookie: A small item of data a browser stores and sends with matching requests according to its attributes and browser rules.