Subdomain takeover check
Find subdomains still pointing at deleted cloud resources that anyone could claim. Checks the first 25 subdomains free.
What this checks
The check finds the domain’s subdomains in public certificate-transparency logs, follows each one’s CNAME chain and, when it lands on a cloud service, checks whether the resource still exists.
- CNAME targets that no longer resolve (NXDOMAIN)
- Provider “not found” pages, such as S3 NoSuchBucket or Heroku “No such app”
- 40 services, including AWS, Azure, Google Cloud, Heroku, GitHub Pages, Shopify, Netlify and Vercel
- The free check covers the first 25 subdomains; a free account checks every domain you add
Questions
What is a subdomain takeover?
When a subdomain still points at a cloud resource you deleted (a bucket, app or site), anyone can create a resource with the same name and serve their own content on your subdomain: phishing pages, cookie theft, or fake downloads.
Does this check claim or change anything?
No. It only reads DNS and makes one normal web request per matched subdomain. It never creates or claims resources.
What does “Dangling (check)” mean?
The record points somewhere that looks gone, but the provider makes takeovers harder (for example by requiring domain verification). Remove the record anyway if you no longer use the service.