June 2025

I was looking for a simple way to require password authentication, and discovered the basic_auth directive for Caddy.

Prerequisites:

All you should need is a server that is running Caddy.

Creating a Password Hash

Before we get started with the Caddyfile modifications, create a hashed version of the password you would like to use using the following command, replacing yourpassword with the password of your choice.

caddy hash-password --plaintext 'yourpassword'

After running the above command, it should return a password hash that looks similar to this:

$2a$14$qls8r/NSs3V5O9hdyJ.EO.kXNaQl5A./QZ.aSOQ0Nit0cjqJtodz2

Note: The above password is the hash for the password, yourpassword. Your password hash will be different. Save this password hash as we will need to add it to the Caddyfile

Creating the Caddyfile

Here is the official caddy documentation Caddyfiles. I will not be going into the basics. So refrence the documentation if needed. This is a simple Caddyfile:

:80 {
    root * /var/www/html
    file_server
}
                

Adding in the basic authentication only requres a few lines. Before your websites file directory and the file_server directive, include the basic_auth directive:

:80 {
    basic_auth * {
        <your_username-here> <generated-hash-here>
    }
    root * /var/www/html
    file_server
    }
                            

That was easy! So that will protect the entire site behind the basic authentication. When since you modified the caddyfile, you will need to restart caddy before you check to see if the login screen worked. You can restart caddy using:

sudo systemctl restart caddy

After doing that, navagate to your webpage, using your IP address or URL in the browser of your choice and you should see a login screen similar to the one below: Congrats! Your whole site is now protected behind basic authentication in Caddy! Just a security reminder, make sure that you have strong permissions on your caddyfile so unauthorized users cannot extract your hash, username, or configuration!

Protecting Specific Files or Directories Behind Basic Authentication

If you have a website that has some public information that doesnt need protected, then some that you want protected behind password authentication (for example, a configuration panel), you can specify which directory paths you want to be protected behind the basic authentication.

:80 {
    root * /var/www/html
    basic_auth /protected/* {
        <your_username-here> <generated-hash-here>
    }
    file_server
}
            

This Caddyfile allows the public to see everything in the website located at /var/www/html with the exception of the files located in the /var/www/html/protected directory. When a user navigates to that directory, they will be prompted for a username and password.

Links That I Found Useful (Some of them were mentioned in the article):

• https://caddyserver.com/docs/caddyfile/directives/basic_auth
• https://caddyserver.com/docs/caddyfile