Web

https://github.com/tomnomnom/waybackurls

https://github.com/anmolksachan/TheTimeMachine (cool project)

https://dnsdumpster.com/

https://crt.sh/

https://www.wappalyzer.com/

https://pentest-tools.com/website-vulnerability-scanning/discover-hidden-directories-and-files

https://builtwith.com/

https://pentest-tools.com/website-vulnerability-scanning/website-scanner

https://pentest-tools.com/information-gathering/find-subdomains-of-domain

https://viewdns.info/

https://viewdns.info/iphistory/

https://dnslytics.com/reverse-ip

https://visualping.io/

https://centralops.net/co/

https://hackertarget.com/zone-transfer/

https://dmns.app/

https://github.com/threatexpress/domainhunter

https://mxtoolbox.com/

https://dnsmap.io/

https://github.com/thewhiteh4t/FinalRecon

https://www.iana.org/whois

https://github.com/projectdiscovery/dnsx

https://www.netcraft.com/

http://web.archive.org/ (history)