How to Set Up Free HTTPS on an Ubuntu Server with Caddy and Docker (Step-by-Step Guide)

Learn how to set up free HTTPS on Ubuntu using Caddy and Docker in minutes. A complete, up-to-date guide for fast and secure servers.

Introduction

If you work on web projects, you already know an SSL certificate is non-negotiable—it’s essential to protect your users’ data and build trust. Traditionally, configuring HTTPS required dealing with Let’s Encrypt, cron jobs, and complex configurations in Nginx or Apache.

Caddy makes this process incredibly simple with automatic HTTPS and certificate renewals out of the box. Combined with Docker, you can deploy it in a clean and reproducible way.

In this guide, I’ll show you step by step how to set up your domain with free HTTPS on an Ubuntu server using Caddy and Docker.

Prerequisites

Before you start, make sure you have:

• Ubuntu 20.04 / 22.04

• Docker and Docker Compose installed

• A domain pointing to your server’s public IP (e.g., yourdomain.com)

• Ports 80 and 443 open

If you haven’t installed Docker yet, you can do so with:

sudo apt update
sudo apt install docker.io docker-compose -y

Step 1: Create the project folder

Create a folder for your Caddy project:

mkdir -p ~/caddy-docker
cd ~/caddy-docker

Inside this folder, you will create:

• Caddyfile: your domain and routing configuration

• docker-compose.yml: the container definition

Step 2: Create the Caddyfile

Create a file named Caddyfile:

nano Caddyfile

Paste this content:

yourdomain.com {
  reverse_proxy localhost:3000
}

• Replace yourdomain.com with your actual domain.
• If your app is running on another port, adjust localhost:3000 accordingly.

Step 3: Create the docker-compose.yml

In the same folder, create docker-compose.yml:

version: '3'

services:
  caddy:
    image: caddy:latest
    restart: unless-stopped
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./Caddyfile:/etc/caddy/Caddyfile
      - caddy_data:/data
      - caddy_config:/config

volumes:
  caddy_data:
  caddy_config:

This setup tells Caddy to:

• Listen on HTTP and HTTPS ports.

• Persist certificates and configuration.

Step 4: Start the container

Launch Caddy with Docker Compose:

sudo docker-compose up -d

Caddy will automatically download Let’s Encrypt certificates. You can monitor the logs with:

sudo docker-compose logs -f

If everything is working correctly, you will see something like:

Server listening on [::]:443
Certificate obtained successfully

Now, open https://yourdomain.com and verify that the certificate is valid.

Step 5: Common issues and fixes

Port 80 already in use

If another service (like Apache) is using port 80, stop it:

sudo systemctl stop apache2
sudo systemctl disable apache2

Domain not propagated

Wait a few hours for DNS to update fully.

Volume permissions

Make sure you run Docker with sudo or add your user to the docker group.

Conclusion

With Caddy and Docker, you now have a secure HTTPS server running in minutes, with zero hassle and automatic renewals.

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