The hosts file is located at the following path on Windows systems:

C:\Windows\System32\drivers\etc\hosts

On Linux/macOS systems, it's located at:

/etc/hosts

This file is a plain text file without an extension.

hosts File

The hosts file is a system file used by the operating system to map hostnames (domain names) to IP addresses, taking precedence over DNS queries. It's commonly used for local network testing, website blocking, and development debugging.

Each line in the hosts file represents a mapping with the following format:

IP_address    hostname(domain)   #comment (optional)

For example:

# You can specify both IPv4 and IPv6 addresses for a domain

127.0.0.1    localhost
::1          localhost

The hosts file typically only contains the 127.0.0.1 localhost entry by default. If modifications cause issues, you can restore the original content.

Common Uses

  • Local Development Testing

    Point domains to local servers (like 127.0.0.1 or 192.168.1.123) for easier website debugging:

    127.0.0.1            myapp
192.168.1.11         api.service
192.168.1.12         mysql.service
    Modifying hosts file for local development testing
    Modifying hosts file for local development testing

  • Blocking Specific Websites

    Redirect domains to 0.0.0.0 or 127.0.0.1 to block access, useful for blocking ads or unwanted sites.

    0.0.0.0   domain-to-block.com  #Block website

  • Bypassing DNS Resolution

    Force domains to resolve to specific IPs to avoid DNS pollution or speed up access.

Modifying the hosts File

On Windows, modifying the hosts file requires administrator privileges:

  1. Open Notepad or another text editor as administrator;
  2. Click File - Open and navigate to C:\Windows\System32\drivers\etc\hosts;
  3. Make changes and save.

On Linux/macOS, you need root privileges:

sudo vim /etc/hosts

Common Issues

  • Access Denied

    Failed to modify hosts file
    Failed to modify hosts file

    Insufficient permissions - run your text editor as administrator:

    Run as administrator
    Run as administrator

  • Changes Not Taking Effect

    If changes don't take effect, you may need to flush the DNS cache:

    On Windows, open CMD or terminal and run ipconfig /flushdns;

    On Linux/macOS, run sudo systemd-resolve --flush-caches or sudo dscacheutil -flushcache

  • Suspicious Configurations

    Malware may modify the hosts file for phishing attacks or network hijacking.