Debug: upstream API calls (click to expand)
How it works
The Subdomain Finder enumerates every subdomain of a root domain that has organic-search visibility, then enriches each one with traffic and link-authority metrics from two independent sources in parallel.
Stage 1: enumerate. For each root domain you submit, we call get-matching-domains on our keyword index. This returns every domain in the index whose host ends in your root (e.g. example.com returns blog.example.com, shop.example.com, www.example.com, etc.). The list is capped per plan at 100 subdomains per root on the Free plan, sorted by descending traffic so the most important subdomains come first.
Stage 2: enrich. For each subdomain in parallel batches, we run two independent lookups:
- Moz fields from our local mirror of
keywordsdb.domains: Domain Authority, Page Rank, Spam Score, Followed Linking Domains, pages-to-subdomain, root-domains-to-subdomain. Free for the project, no external API call. - Traffic + Total Keywords from our keyword index, batched per subdomain. Silent-drop reconciliation handles subdomains the upstream has no data for (rendered as No data, not zero).
Stage 3: compute Website Authority. Each row gets a single 0-100 Website Authority score computed as 0.5 × DA + 0.3 × (PR × 10) + 0.2 × log-scaled-FLD. PR is treated as 0 when missing. Same formula the Website Authority Checker tool uses.
Single vs bulk mode. Single mode takes one root domain in a textbox. Bulk mode takes up to 2 roots per submission in a textarea (each on its own line), with results grouped by root domain in a single table.
Canonicalization. We pass your input through get-matching-domains first to resolve example.com vs www.example.com before enumerating subdomains; otherwise the upstream's response would mix variants in confusing ways.
Plan caps.
- Roots per submission: 2 on the Free plan.
- Subdomains per root: 100.
- Daily-jobs budget: 500 shared with the Domain Authority Checker, Website Authority Checker, and Spam Score Checker.
Known limitations.
- Index-only. Subdomains that don't rank in Google for any keyword (typically staging environments, internal admin panels, or brand-new subdomains) won't appear here. For full DNS-level enumeration, use a dedicated security tool.
- Refresh lag. Newly-published subdomains take a few days to several weeks to enter our index, depending on how quickly Google indexes them and how often we refresh.
- No-data rows. Some subdomains return Moz data but no traffic data (or vice versa) because the two sources have different refresh cadences. The row still shows for transparency, with the missing cells rendered as muted dashes.
What the columns mean
- Subdomain
- The fully-qualified subdomain we found, with no leading
http(s)://. Click to open the subdomain's homepage in a new tab; click the cross-tool icon to inspect it in other tools. - Traffic
- Estimated monthly organic-search visits to this specific subdomain. Same methodology as the Website Traffic Checker. Useful for identifying which of a competitor's subdomains actually drive their traffic.
- Total Keywords
- Count of distinct keywords this subdomain ranks for in Google. Higher means broader topical footprint.
- DA (Domain Authority)
- Moz's 0-100 ranking-strength prediction. Logarithmic, so 30 to 40 is meaningful but 80 to 90 is much harder. Subdomains often have lower DA than their root, because Google generally treats them as separate sites for ranking.
- PR (Page Rank)
- 0-10 score derived from Google's original PageRank algorithm, computed independently. Useful as a second-opinion authority signal.
- WA (Website Authority)
- Our composite 0-100 score blending DA (0.5), PR scaled to 100 (0.3), and log-scaled Followed Linking Domains (0.2). Smooths over cases where DA alone misranks variants.
- Spam
- Moz's Spam Score (0-100). Higher means more spam signals. Useful for spotting subdomains that may carry penalty risk if you're considering acquiring or linking to them.
- Ref Domains
- Count of distinct domains with at least one followed link pointing to this subdomain. The primary measure of off-page link diversity.
- Ref Backlinks
- Total followed backlink count pointing to this subdomain. A single referring domain often produces multiple backlinks; this column counts them all.
- Root Domain (bulk mode only)
- Which of your submitted roots this subdomain came from. Useful when comparing the subdomain footprints of several competitors side-by-side.
Frequently asked questions
How do I find subdomains of a domain?
Enter the root domain (e.g. example.com) above and click Find Subdomains. We query our index for every subdomain we know of (e.g. blog.example.com, shop.example.com, support.example.com) and enrich each one with traffic, Domain Authority, Page Rank, Website Authority, Spam Score, referring domains, and referring backlinks. Bulk mode lets you submit up to 2 root domains in one job on the Free plan.
What is the best tool for finding subdomains?
It depends on what you're trying to do. For security research, tools like Subfinder, Amass, or Sublist3r aggregate certificate-transparency logs, passive DNS, and brute-force wordlists to find every subdomain on a target, including dev / staging / internal endpoints. For SEO research, those tools surface a lot of noise; this tool focuses on subdomains that actually have indexed organic traffic, because that's the subset you can compete with or learn from. Pick the tool that matches the use case.
What is a subdomain?
A subdomain is a domain that sits one level below a registered root. If example.com is the root, then blog.example.com, shop.example.com, and www.example.com are all subdomains. Each subdomain can serve completely different content from a different server, and search engines can rank each one independently. www is the historical default subdomain for the homepage, which is why most sites are reachable at both www.example.com and example.com.
What is the difference between a domain and a subdomain?
The domain is what you register with a domain registrar (the part before the final dot, plus the TLD: example.com). The subdomain is anything you add as a prefix, controlled by your DNS settings rather than your registrar. You can add unlimited subdomains to a domain you own without buying anything new; you just point new DNS records at wherever you want them to resolve.
What is subdomain enumeration?
Subdomain enumeration is the security-research practice of finding every subdomain that resolves on a target, even ones not linked from the public site. Common sources include certificate-transparency logs, passive DNS databases, search-engine indexes, and brute-force wordlists against DNS. This tool only does the search-engine index part: subdomains we've indexed because they show up in organic Google rankings. For full enumeration (including unindexed staging environments), reach for a dedicated security tool like Subfinder or Amass.
Can a subdomain be a separate website?
Yes. Subdomains can host completely different applications, on different servers, with different SEO footprints and different audiences. Google generally treats each subdomain as a separate site for ranking purposes, which is why brand-new subdomains start with a clean SEO slate even on an established root domain. This is part of why subdomain enumeration is useful for SEO: a competitor's blog subdomain might be the actual traffic driver and you wouldn't see that from the root.
Why does the list not match what I see in my hosting panel?
Two reasons. First, we only return subdomains that show up in our organic-keyword index, so a brand-new staging subdomain or one with no public-facing content won't appear here. Second, our index has a refresh lag: subdomains added in the last week or two may not be in the dataset yet. For an authoritative list of every subdomain that resolves on your own infrastructure, your DNS provider's zone file is the source of truth, not this tool.
Do all subdomains rank in Google?
Only the ones that are publicly accessible and not blocked by robots.txt or noindex directives. Staging subdomains (staging.example.com), internal admin tools (admin.example.com), and dev environments typically don't. The subset in our index is the subset that's actually competing for organic traffic, which for SEO research is usually what you want, but be aware it's a filtered view rather than a complete inventory.