Benefits and Restrictions
Benefits of the Hosts File:
(1.) Uses less resources:
By using a function built into your computer, you will be able to block advertising sites (or any other site you wish) without the need for any extra programs. This will cut down on memory and processor usage, which will free up your resources for other tasks.
(2.) Works on connections other than HTTP:
Most ad-blocking programs will only intercept IP calls going to the HTTP (or web) port on your computer. Other transfers can still get through. The Hosts file, however, will block IP calls on any port, whether it is HTTP, FTP, or whatever else you happen to be doing.
(3.) Eliminate many tracking and privacy concerns:
By intercepting the IP calls before they ever leave your computer, the Hosts file can prevent advertising and tracking companies from ever even knowing you are viewing a web page. This will keep them from profiling you and help you keep your privacy. All sites in the Hosts file entered with a 127.0.0.1 address will never be accessed. Sites that are not in the Hosts file may still track you and send you ads. See the notes section for more information.
To find out which advertisers may be tracking you, please visit this excellent web site.
(4.) The Hosts file is configurable:
Rather than relying on others to decide what sites to block for you, you may edit the Hosts file entirely on your own. This means you can put any site you wish into the Hosts file and that site will not be able to be accessed. You can use this to block advertisers, trackers, or sites you would not want your small children to see. You get to decide entirely what you wish to block, and you don't have to depend on someone else's judgement!
(5.) Increased browsing speed:
By placing sites into your Hosts file with their correct addresses, your computer does not need to ask another computer where to find a site. This can significantly speed up your surfing experience because your computer will go straight to that site instead of having to ask directions. Also, by keeping ads from being loaded using the blocking technique in the Hosts file, web pages will be viewable much more quickly since they won't have to load a lot of fancy graphics.
Some restrictions on the Hosts file:
(1.) It will not work with wildcards, such as *.whateveryouwantgoeshere.com.
(2.) It will not work with URL's that begin with IP numbers.
IP numbers are the numerical equivalent of the www.somesitenamehere.com address, and that is what your computer actually uses to find the web page. The names are there so that humans don't have to remember long strings of numbers. You would need to find the www.whatever.com address that the IP number represents, and then block that name instead of using the IP number. For example, Yahoo!'s address is www.yahoo.com, and its IP address is 22.214.171.124 We can block www.yahoo.com but not the IP address. The reason for this is that Hosts is used to determine IP addresses. If we already know the IP address, Hosts will not be consulted and so can not block the site. I do not recommend actually blocking Yahoo! though, as it is a great search engine!
(3.) It will not work with ads that are served from the same site you are viewing.
The reason for this is that the Hosts file must block an entire site, and can not block subdirectories or pathnames on a site. For example, you could not block www.netscape.com/ads/ because you can't block subdirectories. You would need to block the entire www.netscape.com server, and that would leave you without access to Netscape's site. So you will have to use a different method to eliminate ads that come from the site you are viewing, such as an ad-blocking program.
(4.) It may cause some sites to quit working properly.
If you put the wrong server into your hosts file, it may mean that certain websites will no longer be viewable as they normally would be. To remedy this, remove the entry of the site you wish to unblock from your hosts file. Please see the FAQ section for more on this. In particular, you may notice sites that rely on Akamai's servers will not function properly if Akamai is in your Hosts file.