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Subdomain Extractor

A list of full URLs hides the structure you actually care about — which one is the subdomain and which is the root. This free subdomain extractor takes a list of URLs or domains and separates the subdomain, root domain and public suffix for each one, in a single pass.

URLs or domains (one per line)

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What is a Subdomain Extractor?

A subdomain extractor parses a web address and splits it into its domain parts: the subdomain such as www or api, the root domain such as example.com, and the public suffix such as .com, .co.uk or .co.in. It handles common multi-part suffixes so that a URL like mail.example.co.uk is correctly read as the subdomain "mail" with the root "example.co.uk", not "example" with "co.uk".

Knowing the boundaries matters for analytics, DNS, marketing and data cleanup. Analytics platforms want a root domain key rather than a full URL, security teams want to spot suspicious subdomains, and anyone consolidating a domain list wants to group entries by their e-commerce or corporate root. Extracting these parts by hand across hundreds of URLs is error-prone.

This tool works on a whole list at once, outputting a formatted result per line, so you can paste a column of URLs and read the subdomain and root domain for each. The parsing runs locally, so even a sensitive internal host list stays private.

How to use the Subdomain Extractor

Paste a list of URLs or domains, one per line, into the input area.
Click Extract (or the run button).
Read the result: each line shows the original, its subdomain and its root domain.
Use Clear to start over with a fresh list.

Example

Input: https://api.example.com
mail.example.co.uk
example.com

Output:

https://api.example.com → subdomain "api" → root "example.com"
mail.example.co.uk → subdomain "mail" → root "example.co.uk"
example.com → root "example.com"

Common use cases

Normalising a URL list for analytics or reporting by root domain.
Flagging unexpected or suspicious subdomains on a host list.
Grouping many pages by their corporate root to compare traffic or domains.
Cleaning up exported URL data before it goes into a spreadsheet or database.

Pro tips

Paste clean lines — one URL per line and no extra text — so each is parsed correctly.
Hostnames without a scheme are handled for you, so a bare domain like example.com works without adding https://.
Watch for public suffixes: with a multi-part suffix like .co.uk, the tool lands on the correct root only if the suffix is in its built-in list.
Re-run the tool after fixing any line that returns "not a valid domain" so your final list is complete.

FAQ

What is a subdomain?

A subdomain is the part of a domain that appears before the root domain, such as "api" in api.example.com or "www" in www.example.com.

What is a root domain?

The root domain is the name you register, such as example.com, made up of the domain name and its public suffix.

What is a public suffix?

A public suffix is the portion of a domain that is shared by many registrants, such as com, org, or the multi-part co.uk. Recognising it correctly is what stops a tool from reading "example.co.uk" the wrong way.

Does it handle multi-part suffixes like .co.uk?

Yes. The tool includes a list of common suffixes such as co.uk, com.au and co.in, so it correctly identifies the root for these cases.

Does it work on a list at once?

Yes. Paste many URLs, one per line, and each is parsed and returned as its own line of output.

Is it private?

Yes. Parsing happens entirely in your browser, so your list of URLs is never uploaded.

Can I paste URLs without the scheme?

Yes. A bare domain such as example.com is accepted and processed without you needing to add https://.

What happens with an invalid domain?

The tool marks the line as not a valid domain so you can spot and fix it in your source list.