Where is localhost folder located in Mac or Mac OS X?

On Mac and Mac OS X, the localhost folder is located at:

/private/etc/localhosts

This is a configuration file that contains a list of host names that are resolved to the loopback IP address (127.0.0.1). It is used to define names for the local host that are not mapped to any IP address, but are recognized only by the system. This can be useful for testing and development purposes, as it allows you to access services on your local machine using hostnames instead of IP addresses.

Note that the localhost folder is a virtual folder and does not physically exist on your computer. It is used as a reference by the operating system and applications to access the local host.