Subdomain Finder

The Subdomain Finder is a free online tool that check 24 common subdomains using dns-over-https. find active subdomains for any domain — useful for seo site structure analysis and security audits.. It runs entirely in your browser with no installation or sign-up needed.

This tool checks 24 common subdomain names (www, mail, api, blog, shop, admin, etc.) by looking up their DNS A and CNAME records using DNS-over-HTTPS via Cloudflare.

Yes. If a CNAME record points to an unclaimed external service (like a deleted Heroku app or GitHub Pages), an attacker can register that service and take over your subdomain.

This tool checks 24 common subdomains. For full enumeration, use tools like Subfinder, Amass, or SecurityTrails which check thousands of subdomain patterns.

Yes, the Subdomain Finder is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The Subdomain Finder processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Subdomain Finder is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Subdomain Finder in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The Subdomain Finder works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

A subdomain is a prefix that points to a distinct host, like blog.example.com, while a subdirectory is a path on the same host, like example.com/blog. The key difference is technical: a subdomain has its own DNS record and can live on a separate server, IP, or platform, whereas a subdirectory shares the root domain's server and configuration. For SEO this matters because search engines often treat subdomains as somewhat separate sites, so authority does not always flow as freely as it does between folders on one domain. Subdirectories are usually preferred for content you want to consolidate under one brand, while subdomains suit genuinely separate services like apps, status pages, or staging environments. This tool detects active subdomains by DNS lookup, so you can map exactly which prefixes a domain is running before planning your structure.

An A record maps a hostname directly to an IPv4 address, so www.example.com pointing to an A record means it resolves straight to a numeric IP. A CNAME record instead aliases one hostname to another hostname, so app.example.com with a CNAME might point to a platform like a hosting provider, which then resolves to the final IP. This tool checks the A record first for each subdomain and falls back to the CNAME if no A record exists; either response means the subdomain is active. The distinction is useful because a CNAME target often reveals which external service sits behind a subdomain, such as a status-page host or a deployment platform, while an A record just shows the IP. Enter a domain above and the results display the resolved IP or CNAME target for every active subdomain found.

The most common reason is that this tool checks a curated list of 24 common subdomain names, so any prefix outside that list, such as internal-billing or a custom label, will not be tested and therefore will not appear. A subdomain can also show as not found if it has no public A or CNAME record, for example one that only resolves on an internal network, or if it uses a record type the scan does not query, like an AAAA-only IPv6 host. Temporary DNS propagation delays or resolver caching can occasionally hide a very recently created record too. If you need a name that is not on the common list, a dedicated enumeration tool like Subfinder or Amass that pulls from certificate-transparency logs will go deeper. For a fast first pass on the usual suspects, run your domain through the scanner above.

Subdomains do not automatically hurt SEO, but they can dilute results if used carelessly. Search engines treat a subdomain as a related yet somewhat separate entity, so signals like links and authority do not always pass between blog.example.com and the root domain as cleanly as they do between folders on one host. The bigger practical risk is a forgotten staging or dev subdomain that is accidentally indexable, which can leak duplicate content and waste crawl budget. The fix is to find those hosts, then add a noindex rule or block them in robots.txt. Legitimate subdomains for genuinely distinct services, such as an app, store, or support portal, are perfectly fine when each is intentional and properly configured. Scanning your domain here gives you a quick inventory of every live subdomain so you can decide which to consolidate, secure, or de-index.

A CNAME target is often the most revealing line in a subdomain's DNS record because it names the external service the subdomain points to rather than just an anonymous IP. If status.example.com has a CNAME pointing to a hosted status-page provider, or app.example.com aliases to a deployment platform, the target instantly tells you which third party is running behind that host. This is valuable for two reasons. For infrastructure mapping, it shows which services a domain depends on without any guesswork. For security, a CNAME pointing to an unclaimed or deleted external service is the classic setup for subdomain takeover, where an attacker re-registers that service and serves content from your subdomain. This tool surfaces the CNAME target alongside each active subdomain, so enter a domain above to see exactly where its aliases lead.