If you work in web development,
proper editing of a hosts file allows you to redirect someone to a different
URL. This might be useful is you have a website under development that
exists at domain name that has the same name as an existing website. Some
simple editing of the hosts file on a target computer will send the user of
that PC to the correct website. I’ll show you the steps needed to accomplish
this a bit later in this article.
You can also edit the hosts file to block
users from visiting certain websites. Manually editing hosts files for
hundreds (if not thousands) of machines isn’t an ideal solution, as there are
more effective third-party tools available that can do that more easily. It’s a
good skill to learn how to do manually, however, so I’ll show you how to do that
as well.
What
is in the hosts file?
A hosts file contains text
information that maps IP addresses to desired host names. Regardless of whether
the hosts file exists on a Windows, Linux, or Macintosh machine, the contents
will be the same: IP addresses are listed on the left, followed by the host
name that the IP address on that line should be mapped to. If you’re an
overly-organized type you can neatly line up your columns of IP addresses and
host names, but you don’t need to: As long as the IP address and host name are
separated by at least one blank space the mapping will work. You can also
insert comments into the hosts file using the ‘#’ symbol, which can be helpful
in documenting why changes were made to the host file, especially for someone
else who may not be familiar with why the changes have been made.
As an example, here’s a photo
showing a sample local hosts file loaded into Windows Notepad on a Windows 7
PC.
Where
is the hosts file?
In most Windows OSes, the HOSTS file
is located in the following file directory found in the Windows\System32
folder:
1
|
C:\Windows\System32\Drivers\etc
|
Note: The etc folder may be hidden on your system, so you may
need to show hidden files and folders. For information on how to do this with
Windows 7.
How
to edit the hosts file
The hosts file is a simple plain
text file, so you can use the default Windows 7 Notepad application to edit the
file. I’ll show you how to find, load, edit, and save the file in this section.
Scroll down a bit farther in this article to see specific instructions on how
to edit a hosts file to redirect URLs or how to block websites.
1. Click on the Start button,
then All Programs, and then Accessories. Find the Notepad
application.
2. Right-click on the Notepad
application icon and select Run as Administrator from the menu that
appears (see example below). You may get a User Account Control (UAC) warning
after doing so; just click Yes on the windows that appears to accept changes.
3. After Notepad has loaded,
navigate to the C:\Windows\System32\Drivers\etc directory.
4. If you’re not seeing any files in
the etc directory (see below), it’s because all of the files here don’t have
any file extensions, and Notepad is only looking for files with .txt
extensions. To fix that…
5. …select ‘All Files’ from the drop-down
in the lower right corner of the open window. This will then display all the
files in the directory, as shown below.
6. Double-click on the hosts file to
load it into notepad.
7. Once you’ve made your edits,
overwrite the existing hosts file and make sure that you haven’t accidentally
added a .txt extension to the file. The hosts file needs to remain exactly that
— it should keep with the hosts file name with no extensions whatsoever, or the
OS won’t recognize the file.
Editing
the HOSTS file to redirect to a specific URL
One of the most popular uses of editing
a hosts file is to direct a user to a website that may have a web address that
conflicts with an existing one. For example, let’s say you work at a company
that makes petri dishes, and your web development team has an internal website
that use the web address www.google.com. In order to
redirect the user to your internal website when they type Petri.com, have the
user load up the hosts file and make the following edits:
1. At the bottom of the hosts file,
add the correct IP address for your internal site followed by at least one
space, as shown below.
2. This one-line change will tell
the user’s PC to use the new IP address mapping for the Petri.com web address,
which will now be redirected to the correct site.
You can also edit a hosts file to
give users access to a site that they can’t normally reach by typing in a URL.
For example, you may have a beta.petri.com site that shows the design for your
new website design, but you want to limit access somewhat. Adding the IP
address followed by the beta.petri.com address will allow users who type in
beta.petri.com to reach the correct site, but users who don’t have the updated
host mapping won’t be able to find the site, unless they know the IP address.
Once you’ve made the required
changes, simply save the file (as described in the previous section), reboot
the user’s PC, and when the user attempts to access both the normal and beta
Petri sites they’ll be routed to the correct locations.
Editing
the HOSTS file to block websites
Another popular use for editing the
hosts file is to block the user from accessing specific sites. For
example, if you want to prevent a user from accessing Facebook on their
company-supplied PC, you could follow these steps:
1. Load up the hosts file
of the target PC and add the localhost IP address of 127.0.0.1, followed by at
least one space, and then the Facebook addresses you want to block, as shown in
the example below.
Using the steps outlined here, you
now have the knowledge necessary to both redirect someone to a different
website and to also block their access to specific websites. We have a number
of other how-to guides that cover the same topic for different platforms and
operating systems.
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