OSINT for opensource intelligence refers to the using of common tools to gather information about a service. Here is a complete compilation of some of the tools hosted online.
8 Great subdomain finder (Hosted online)
- Sublist3r
- DNScan
- Anubis subdomain finder
- Amass Subdomain finder
- Nmap(dns-brute-script)
- Lepus subdomain finder
- Censys
- Findomain(fastest)