IANA RFC8615 defines a “.well-known/” folder for web servers to put metadata fundamental to a web server’s organization, policies or contact information. Several popular files are seen under public website https://example.invalid/.well-known/ directory.

keybase.txt

verify ownership of domain for Keybase.io

security.txt

security incident contact info

dnt-policy.txt

Do Not Track Policy statement

humans.txt

author information