example.com, blog.example.com and https://blog.example.com/guides are related, but they are not interchangeable. The first is a registrable root domain, the second is a hostname containing a subdomain, and the third is a complete URL.
Choosing the wrong boundary can distort an audit. Collapsing every hostname hides infrastructure. Keeping every hostname can make one organization look like dozens of independent websites. The domain extractor supports both views so the output can match the question.
The three terms in one example
| Term | Example | What it identifies |
|---|---|---|
| Root or registrable domain | example.co.uk | The name registered beneath a public suffix |
| Subdomain | support | A label controlled beneath the registered domain |
| Hostname | support.example.co.uk | The complete host used by a network service |
| URL | https://support.example.co.uk/login | A specific resource and access method |
The visual guide to domain-name parts explains labels and suffixes in more depth. The key point is that the root boundary cannot be inferred by counting dots. In example.co.uk, the public suffix contains two labels.
When should you extract root domains?
Use root domains when you need one record per registrable website or organization. This is usually the right choice for referring-domain counts, prospect grouping, competitor lists and broad ownership research.
- Ten links from different pages on
news.example.combecome oneexample.comrecord. shop.example.comandblog.example.comare grouped together.- Frequency counts show concentration without producing duplicate rows.
When should you keep full hostnames?
Use hostnames when the labels before the root domain carry operational meaning. Migration teams need to distinguish a storefront from an API. Security analysts may need the exact suspicious host. International sites may separate markets with uk.example.com and ke.example.com.