These tools can help you expand your understanding of the subdomains associated with a particular domain, and can provide valuable insights for security, SEO, and other purposes. As always, it’s essential to use these tools ethically and responsibly and to obtain permission before conducting any reconnaissance activities on someone else’s domain. Subdomain Finder, There are several subdomain finder free tools available. Here are some popular ones:

1. Sublist3r – A Python-based tool that uses various search engines and web archives to find subdomains. It’s available for free on Github.
2. Amass – A command-line tool that uses a variety of sources, including DNS, web archives, and search engines, to find subdomains. It’s available for free on Github.
3. DNSDumpster – A web-based tool that uses DNS records to find subdomains. It’s available for free at dnsdumpster.com.
4. Fierce – A command-line tool that uses DNS zone transfers to find subdomains. It’s available for free on Github.
5. Recon-ng – A reconnaissance framework that includes a subdomain module for finding subdomains. It’s available for free on Github.
6. SubFinder – A tool that uses passive online sources to find subdomains, and can also perform active scanning to identify live subdomains. It’s available for free on Github.
7. FindSubdomains – A web-based tool that uses a variety of sources, including SSL certificates and DNS records, to find subdomains. It offers a limited free version and a paid premium version.
8. Knockpy – A Python-based tool that uses a dictionary-based approach to find subdomains by brute-forcing them. It’s available for free on Github.
9. SubDomainizer – A Python-based tool that uses web scraping and other techniques to find subdomains. It’s available for free on Github.
10. Aquatone – A reconnaissance tool that includes a subdomain module for finding subdomains using various sources, including DNS and web archives. It’s available for free on Github.

Read more : Subdomain Finder and Security Vulnerabilities

These tools can help you discover subdomains associated with a particular domain, which can be helpful for security, SEO, marketing, and other purposes. However, using these tools ethically and responsibly and obtaining permission before conducting reconnaissance activities on someone else’s domain is essential.

Here are some other online/web-based subdomain finder tools you may find helpful:

1. Pentest-Tools.com Subdomain Scanner – A web-based tool that brute forcers and other techniques to find subdomains associated with a domain. It offers a limited free version and a paid premium version.
2. SecurityTrails Subdomain Finder – A web-based tool that uses a variety of sources, including DNS records and SSL certificates, to find subdomains. It offers a limited free version and a paid premium version.
3. DNS Checker – A web-based tool that can perform DNS lookups to find subdomains associated with a domain. It’s available for free at dnschecker.org.
4. Spyse Subdomain Search – A web-based tool that uses various sources, including DNS records and SSL certificates, to find subdomains associated with a domain. It offers a limited free version and a paid premium version.
5. Virustotal – A web-based tool that can be used to find subdomains associated with a domain. It uses a variety of sources, including DNS records and SSL certificates, to provide information about the environment and its subdomains. It’s available for free at virustotal.com.

These tools can help you identify subdomains associated with a particular domain and provide valuable insights for security, SEO, and other purposes. It’s essential to use these tools ethically and responsibly and obtain permission before conducting reconnaissance activities on someone else’s domain.