A text file in a TCP/IP network that specifies the IP addresses of computer names and domain names. It is used to convert a request by name to a numeric IP address on the local network or the Internet.
Testing and Quick Retrieval
HOSTS files are used to override the DNS system for testing purposes so that a Web browser or other application can be redirected to a specific IP address. In addition, by explicitly stating an IP address in a HOSTS file, a website can be retrieved more quickly, because the multiple transmit/receive steps a normal DNS query takes have been eliminated. See DNS
Denying Access to Websites
websites can be denied access from a computer if the URLs of those sites are added to the HOSTS file and directed to the loopback address of 127.0.0.1. For example, the following entry in a HOSTS file prevents users from reaching YouTube or eBay.
HOSTS File Locations
In Windows, the HOSTS file is in the \windows\system32\drivers\etc folder. In the Mac, it is in /private/etc. The first line of a HOSTS file contains the following. See localhost