It is often used to block access to websites or servers, to redirect requests to a new or local server, or by malicious attackers who redirect websites to honeypots and fake websites. Web developers can use the hosts file to work on moved websites before the DNS propagates.

The concept is pretty simple: When you move your website to a new host, you need to tell the DNS system that your domain name is now accessible on a different IP address. This DNS propagation takes up to 48 hours. When you load the website before propagation you automatically load it on the old server and not the new one. This can be problematic for web developers who want to check if the website displays correctly and without errors on the new server. That’s where the host file comes in. You basically force your computer to use the new IP address instead of the old one to open the domain name in the web browser.

Check out our [block]2[/block] for a selection of programs that allow you to work with the hosts file.

The Firefox extension Change Hosts adds those controls, and a lot more to the web browser. Many web developers use the Firefox browser, as it offers access to great web development tools such as Firebug. With Change Hosts installed, they can change hosts files with two mouse clicks.

When you first install the extension you will notice that it adds information to the status bar of the browser. Here you see the name of the active hosts file and the current server IP.

A right-click opens a context menu that displays all available hosts files in a menu, options to flush the Dns Cache, and to open the extension preferences.

The general tab displays whether the hosts file is readable and writable on the system, options to run another local file after changing hosts file, and whether pages should be automatically reloaded when a new hosts file is loaded.

The Definitions tab offers options to add, edit and remove hosts file. Hosts files can be edited right away in a basic text editor in the browser, and changes become available immediately after they have been saved. It is furthermore possible to copy and paste information from one hosts file to another, or from the clipboard directly into a hosts file.

Change Hosts is a great extension for web developers that work with the Firefox web browser. The ability to maintain multiple hosts files, for instance for different projects, plus the ability to flush the DNS cache from within the browser are useful features. Firefox users can download and install the latest version of the extension from the official Mozilla Firefox Add-ons repository.

It is relatively uncomfortable to add, remove or edit large hosts file in a text editor. Software often offers better manageability and sometimes even additional features like flushing the DNS cache or optimizing the hosts file by removing duplicates.

All programs mentioned in this overview are freeware, most portable that require no installation.

Hosts Man

Hosts Manager has been around for a very long time. It is one of the most sophisticated, feature rich programs for hosts file editing. It’s feature set include everything one could be looking for, from downloading popular hosts lists from the Internet over hosts file optimization to remove duplicates to a hosts file editor and backup options.

It is possible to use multiple hosts file lists from the Internet and merge them into one big list sans the duplicates easily with Hosts Man.

• Homepage: http://www.abelhadigital.com/hostsman

Host Profiles

A new software program that adds the option to run multiple hosts file on a system. Users who work with Host Profiles can switch between different hosts files. This basically replaces the existing hosts file with another file. One possible option would be one hosts file for web development, and one for general Internet surfing, or browser specific hosts files.

The editing capabilities are limited to plain text editing. The program has controls to flush the DNS cache, and display the current hosts file.

• Homepage: http://hostprofiles.codeplex.com/

Advanced Hosts Editor

The program offers some of the best editing capabilities of all hosts file managers. Problem is that it is currently offered as a beta version which does not play well with large hosts files. Users will get an unresponsive window when they try to load the program for the first time.

Advanced Hosts Editor is well suited for users with a hosts file that has a few hundred entries. The software displays all hosts and websites that have recently established a connection with the computer, which makes it an effective tool for users who want to add servers to their hosts file while they are using the Internet.

The hosts file size limitation is the biggest drawback of the application.

• Homepage: http://ahe.devs-on.net/en/

HostsXpert

HostsXpert is a regularly updated hosts file manager that offers editing and handling of the file in Windows. It supports backup and restoration of the hosts file, and can download a popular list from MVPs and HP.

Editing is not as straightforward, everything is displayed in forms which means it takes longer to edit multiple entries than it would be in programs that display the entries in a text editor like interface.

• Homepage: http://www.funkytoad.com/index.php?option=com_content&id=13

Hosts Manager

Hosts Manager can be used to switch between multiple hosts files in Windows. The program is not an hosts file editor, which is probably the biggest weakness. It is also the only program that requires installation and the Microsoft .NET Framework 3.5.

• Homepage: http://sourceforge.net/projects/hostsmanager/

Closing Words

Did we miss a hosts file software? Let us know in the comments.

The Windows Hosts file can be used to block or redirect hostnames. A hostname is the core part of a web address or local address, for instance ghacks.net or localhost. Each hosts file entry specifies an IP address and a hostname, which basically tells the system that the hostname should be resolved with that IP address.

The DNS server, that is usually queried, is bypassed for all entries in the Hosts file. Let me give you two examples where this may be beneficial. Users could block known advertising companies or spammers by redirecting requests to the local PC. This basically loads nothing when a website tries to load an advertisement, popup or other element.

Another example are web developers. Say you just moved your website to a new server and the IP changed in the process. DNS servers need up to 48 hours to propagate, which means that it is difficulty to test the website on the new server after the move if the DNS server is still redirecting the request to the old server. The web developer could assign the new IP address to the website to avoid the propagation issue. (Please see Work On Websites Before DNS Propagation for a detailed guide on that subject)

It has to be noted that the Hosts file can also be exploited by malicious software, either by redirecting the user from legit sites to questionable ones, or by blocking access to security software that they might need to remove those programs again from the PC.

The location of the Windows Hosts file

The Windows Hosts file is located under the following path:

%SystemRoot%\system32\drivers\etc\

The %SystemRoot% in the beginning is a variable that is set to the Windows directory. Most Windows users have installed the operating system on c:\windows which would mean that the hosts file can be found under c:\windows\system32\drivers\etc\hosts

It may be necessary to display hidden system folders if Windows Explorer is used to navigate to the folder. A click on Tools > Folder Options in Windows Explorer and a switch to the View tab opens a configuration menu where hidden folders can be set to be revealed. Locate “hide protected operating system files” and “hidden files and folders” and make sure that the former is unchecked, and that the latter is set to “Show hidden files, folders and drives”. The settings can be easily reversed this way when needed.

The Hosts file itself can be edited with any plain text editor, Notepad for instance which ships with Windows. You should check first if the Hosts file is write protected. This is done by right-clicking the file and selecting properties from the opening context menu.

Look at the attributes section of the General tab. The file is write protected if read-only is checked. If it is, remove the entry. If you keep the read-only setting it is not possible to edit or reset the hosts file. Remember to set the read-only attribute again once you are finished to prevent third party editing of the hosts file.

The default Windows Hosts file has no active entries. Please note that a line beginning with # is a comment line which will not be executed or processed.

Editing the Windows Hosts file

Take a look at the examples in the comments. The syntax is always the same, first the IP address that you want to redirect the hostname to, then the hostname separated by at least one space.

• To add entries to the hosts file you would enter the IP address first in the next blank line, followed by a space (or by pressing tab) and the hostname (which can be a domain name or localhost).
• To delete Windows Hosts file entries select the whole line and press the delete button on the keyboard.
• To edit individual entries click in the line of the mapping that you want to edit and make the changes.
• To reset the hosts file simply remove all lines that are not comments. Microsoft has created a Fix-Ii solution to reset the hosts file which can be used instead. Users just have to execute the program once they have downloaded it to the local system. The main benefit is that they do not need to go through the manual process this way.

Please note that you need to save the changes before they become available. In Notepad you would select File > Save from the menu to do that.

And that’s how your edit and reset the Windows Hosts file. Please leave any open questions or comments in the comment section below.

The Windows hosts file is basically a text document that lists IP addresses on the left and hostnames on the right. The hosts file is located in system32/drivers/etc/ of the Windows folder. It can be edited with any text editor.

Optimizing the hosts file can speed up the parsing of the file and keep the DNS client service enabled while using a big hosts file.

The hosts optimizer will automatically remove duplicate host names from the hosts file, remove all comments including entries that have been made a comment to disable them and put a maximum of nine host names in a single line if they point to the same IP address.

The program will automatically created a backup of the hosts file before optimizing it. It has to be noted that the DNS cache needs to be flushed whenever a change is made to the Windows hosts file if the DNS Client service is enabled.

Hosts Optimizer can be downloaded from the abelhadigital forum. The program is also part of the hosts manager HostsMan.

An entry in the hosts file ensures that the website is opened at the new IP making it possible to work with it there to ensure that it displays properly in that location (read Work On Websites Before DNS Propagation for an in depth article about that).

There are several other web design related tasks that make the hosts file valuable to the web designer and webmaster. It can for instance be helpful when a web designer works on a website that is referencing external scripts which can be redirected to localhost for testing (or avoiding timeouts).

Hosts Manager is an Open Source program that can be used to work with multiple host files on a computer system. This gives the user of the system better control over the process. It is for instance possible to create one hosts file for local web design purposes and one for Internet use.

Hosts Manager displays an icon in the Windows system tray upon startup that can be used to switch, create, edit and delete hosts files.

Creating a new hosts file or editing an existing one will open that file in the default text editor of the system. All newly created files contain all entries of the default hosts file by default which can be edited in the text editor easily.

Hosts Manager requires the Microsoft .net Framework 3.5. It will run on most Windows operating systems including Windows 7 and Windows Vista. The download is available at the project’s homepage over at Source Forge.

And then there are programs like Inoculate that use the hosts file of the operating system to block spyware websites from being opened by routing the address of the spyware website to the local computer system (which means the website will not be displayed when the user tries to open it).

Inoculate is a portable software program for the Windows operating system that will add more than 14000 spyware websites to the Windows host file. These 14000 spyware websites are blocked from being accessed by users of the computer system. The software creates a backup of the current host file before it begins to add the spyware websites to it so that spyware attacks and spyware programs are automatically blocked.

It is possible to reset the Windows hosts file or restore a previously created backup. One slight disadvantage of this spyware blocking approach is that it is not possible to view the spyware websites before they are added to the hosts file. Another problem is that the program is not automatically updating the spyware list over the Internet which alternatives like Hostsman which offers four different block lists and auto updating. Hostsman on the other hand is not a portable software program.

It would be nice if the developer of Inoculate would add an auto update option and the ability to load different hosts file lists into the application.