Subdomain Extractor

The Subdomain Extractor scans a list of URLs and pulls out the subdomain portion of each host, the label or labels that sit in front of the main domain, such as the blog in blog.example.com or the api in api.staging.example.org. It returns a deduplicated table of subdomains with a count of how many URLs used each one, giving you a fast overview of the site structure hidden inside a link list.

It is aimed at security researchers, SEO specialists, and developers who need to understand how many distinct subdomains a set of URLs touches. Enumerating subdomains by hand is tedious and error prone, especially across hundreds of links, so this tool automates the split and lets you focus on interpreting the results rather than parsing strings.

Processing is entirely local to your browser, so nothing you paste leaves your device. Because subdomains often reveal internal services, staging environments, and regional hosts, keeping the data private matters, and this tool never uploads or stores the URLs you analyse.

Features

• Isolates the subdomain labels in front of the main domain for each URL in your list.
• Handles multi-level subdomains such as api.staging.example.com without losing any of the leading labels.
• Deduplicates subdomains and counts how many URLs reference each one across the whole input.
• Skips plain domains that have no subdomain by default so your results stay focused and relevant.
• Offers an option to include apex-only hosts, labelling them clearly when you want a complete picture.
• Sorts the output by frequency so the busiest subdomains appear at the top of the table.
• Exports the subdomain table to CSV or XLSX, or copies it to the clipboard for reporting.

How to use Subdomain Extractor

1. Paste your list of URLs into the input box, one per line or separated by spaces.
2. Leave the default behaviour to skip hosts that have no subdomain, keeping the list focused.
3. Enable the include-apex option if you also want to see how many URLs used a bare domain.
4. Read the table, where each row shows a unique subdomain and how many URLs referenced it.
5. Review the stats to gauge how many subdomains a link list spans and which are most common.
6. Export the subdomains to CSV or XLSX, or copy them, for security reviews or documentation.

Benefits

• Security researchers map the subdomains present in a scope or scan output within seconds.
• SEO teams understand how content is distributed across a site's subdomains from a URL export.
• Developers spot staging, API, or regional hosts hidden inside a large collection of links.
• Analysts quantify how many distinct subdomains a dataset touches without manual parsing.
• Anyone auditing links gets a clean subdomain inventory rather than a repetitive URL dump.
• Local processing keeps internal and staging subdomains private on your own machine.

A hostname is read from right to left: the rightmost labels form the main domain and top-level domain, and anything in front of them is the subdomain. For example, in shop.eu.example.com the example.com part is the main site and shop.eu is the subdomain. This tool takes everything before the final two labels as the subdomain, which works cleanly for the vast majority of everyday hosts.

Because some sites use multi-part top-level domains such as co.uk, a simple two-label rule can occasionally treat part of the registrable domain as a subdomain. The tool favours simplicity and predictability over a giant public-suffix database, so for hosts on compound TLDs you may want to sanity-check the results. For the plain domain names themselves, use the Domain Extractor from URLs.

All parsing happens in your browser with JavaScript, so your URLs are never uploaded, which is important because subdomains frequently expose internal tooling, environments, and infrastructure. The include-apex option lets you account for links that point straight at the bare domain, so you can see the full distribution between subdomained and root-level URLs in one place.