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 verifies ownership of domain for Keybase.io. security.txt gives security incident contact info. dnt-policy.txt contains the Do Not Track Policy statement. humans.txt is for author information.