HOSTS File, Explained: The Location and How to Use It to Block Unwanted Websites

You might have heard of a computer’s hosts file. If not, you didn’t miss much. Literally, that’s a file named “hosts”.

Unlike computer files in general, this file has no extension that determines what type it is. So, the file itself is generally inconsequential. You can create one for the hell of it.

However, when placed at a particular location within your computer, it can be an effective tool to control a computer’s access to the outside world—the Internet. In this case, I’d refer to it as the HOSTS file (cue spooky music). The file is not case-sensitive, but most of the time, you’ll find it in all lower case.

If you’re interested in simply and effectively blocking certain websites from a computer or are curious about what sort of sorcery this is, you’re reading the right post.

I’ll explain how the HOSTS file works, its location, and a quick way to edit it on your computer, whether it’s Windows or Mac.

Dong’s note: I first published this post on April 12, 2022, and last updated it with the latest information on April 10, 2025.

What the HOSTS file is, and how to handle it

Every computer running Windows, macOS, or Linux has its HOSTS file. By default, this file is not in effect. It’s there, but it doesn’t do anything other than contain brief information on what it is and how to use it.

In other words, you can delete the default HOSTS file, and nothing will happen. We don’t need it. And we can always recreate it.

Understanding the HOSTS file

When edited in a certain way, the HOSTS file works as the computer’s local DNS mapper. It’s a manual way to map a domain, such as facebook.com, to a particular IP address of your choosing.

The HOSTS file was the original way of binding a domain with an IP address in the early days of interconnected computers—the foundation of the Internet—before the DNS server came into existence.

So, when you map a domain to a non-existing IP address or that of the computer itself, you effectively block the domain for the computer’s users.

Here’s an example of an entry in the HOSTS file:

127.0.0.1     www.facebook.com    #facebok is a waste of time

The format of the line is known as the command syntax. In this case, it’s:

IP address (space) domain (space) #(optional)

A couple of things to note:

• The part starting with # is optional. It’s a comment.
• We only need a single space to separate the IP address and the domain, or the domain and the optional comment. But for clarity, you can use multiple spaces or the Tab key on the keyboard.
• The domain should match that of the actual website—some include the “www.” part, others don’t, as in www.facebook.com vs. facebook.com. To be sure, you can use a separate entry for each.

This particular example entry binds www.facebook.com to the IP of the localhost, the computer itself, and in effect, blocks the computer’s access to Facebook. Specifically, when you go to facebook.com, you’ll get a message that the website doesn’t exist or is unavailable.

Alternatively, you can also use 0.0.0.0 as the IP address to get the same effect. And if you use the IP address of another website, the entry becomes a mean prank or a (malicious) hack.

This mapping takes effect system-wide and immediately, meaning it will affect all user accounts of a computer, and you don’t even need to restart the computer.

The way it works, every time you want to reach a domain, such as entering it on a browser, the computer will check its HOSTS file for the mapping, and if the domain is manually mapped, it’ll use that and no longer query a DNS server for the domain.

And you can manually map as many domains as you’d like—as long as you know what you’re doing and don’t abuse it.

Within the HOSTS file, each mapping entry (each domain) takes one line. You can map multiple domains to the same IP. So use 0.0.0.0 or 127.0.0.1 if you want to block all of them.

With that, let’s find out where this glorious HOSTS file resides on your computer and how to edit it.

How to handle the HOSTS file on a Windows computer

On a Windows computer, the HOSTS file always resides at this location:

c:\windows\system32\drivers\etc\

In the rare case where Windows is installed on another drive instead of c:, change the drive letter accordingly.

Copy and paste that line into the address bar of Windows Explorer and hit Enter to quickly reach the location, as shown in the screenshot above.

Now you can manage the file however you do any file, including deleting, renaming, or making a copy of it. By the way, if you move the HOSTS file to another location, it no longer has any effect.

It takes some work to open and edit the HOSTS file. Since it has no extension, the usual double-clicking won’t work. Plus, you need to open it with administrator privileges to make changes—otherwise, the file is read-only, and you can only view the content.

But generally, you can open it the way you open any file using a text editor, such as Windows’s built-in Notepad app.

If you’re unfamiliar with the app or don’t know how to handle files in general, the fastest way to open the HOSTS for editing in Windows is to open it via an elevated Command Prompt—again, you won’t be able to save the changes otherwise.

Here are the steps (as shown in the screenshot below).

1. Run elevated Command Prompt

• Type “cmd” (no quotes) into the search field on (or under) the Start Menu
• As Command Prompt appears in the result, right-click on it and choose “Run as administrator”.
• Answer the security prompt, if any, affirmatively.

The Command Prompt window will appear.

2. Open the HOSTS file in Notepad:

Copy and paste the following command into the Command Prompt window and hit Enter:

notepad c:\windows\system32\drivers\etc\hosts

That will open the file in Notepad for editing.

3. Edit the file and save the changes

• Enter domains you want to block following the syntax mentioned above, one domain per line, as shown in the last two lines in the screenshot. (Hit Enter each time you want to create a new line.)
• If you no longer want to block a domain, remove the entire line.

Once done, save the file. (Use the Ctrl+S keyboard combo, or just close the file and choose to save when prompted.)

Mission accomplished. The blocking will take effect immediately.

By the way, the HOSTS file shares the same syntax across platforms. Consequently, you can use the same file for Windows and macOS. Or you can copy the content of the file between them.

How to handle the HOSTS file on a Mac

The HOSTS file is generally hidden in the /private/etc/ folder on a Mac.

Here are the steps to locate the HOSTS file on a Mac, as shown in the screenshot above:

1. Bring Finder to the forefront by clicking a blank spot on the desktop, then choose Go -> Go to Folder…
2. Enter /private/etc/ in the field and hit Go.
3. Locate the HOSTS file in the folder that appears. If it’s not there, you can make a new one or copy one over from another computer.

But if you want to edit the file, you can skip the above.

Here are the steps to open the HOSTS file on a Mac for editing

1. Run Terminal (use the Spotlight to search for it), and enter the following command (then press Enter):

sudo nano /etc/hosts

You’ll be asked to enter the password for the current account. Do it!

Similar to the case of Windows above, you must use an admin-level account to be able to make changes to the HOSTS file on a Mac.

2. The HOSTS file will be open in the Nano app. You can now use the arrow keys to move around and enter the information as needed.

After that, use Ctrl+0 to save the changes and Ctrl+X to exit. Mission accomplished.

Be careful with pre-made HOSTS files

Using the HOSTS file is a sure way to control the binding of a domain to an IP address on a computer, and all that applies. Consequently, it’s a straightforward and effective method to block certain websites from the machine.

Entering one domain at a time into the HOSTS file can be time-consuming. For this reason, there are many pre-made HOSTS files, where somebody has compiled a long list of blocked domains, available for download.

However, be careful with these pre-packaged HOSTS files. They tend to include hundreds of domains to block all kinds of things, including legitimate services. Not to mention, there can be malicious entries.

Many domains are interconnected, and blocking one can prevent others from working properly. Blocking the wrong domain can also cause important computer functions, such as auto-updates or security/integrity checks, to stop working.

On top of that, a large HOSTS file can also adversely affect performance. It’s a good idea to keep its size below a few hundred kilobytes. Generally, you should only use entries that you’re aware of in the HOSTS file.

The final thoughts

The HOSTS file is a prime example of a double-edged sword.

It’s a great tool when used properly for the right purpose. But it can also be a pain when you abuse it or are not aware of it. It can cause many unexpected connection issues—it’s like a phonebook that has been deliberately altered.

It’s a good practice to be mindful of this file and use a blank (default) HOSTS file when troubleshooting your connection or connection-related issues. When in doubt, you can safely disable the file by renaming, deleting, or moving it away from the default location.