pentest-tools.com

Pentest-Tools.com provides over 25 deeply integrated security testing tools and reliable automation features that eliminate 80% of manual work. Pentest-Tools.com enables quick detection and reporting of vulnerabilities in websites and network infrastructures. The available tools enable you to scan your website, scan your network, discover the attack surface and many more. Find Subdomains is a free tool that discovers subdomains and determine the attack surface of an organization.

LINK: https://pentest-tools.com/reconnaissance/find-subdomains-of-domain