---
title: caddy — automatic HTTPS web server
date: 2026-10-18
time: 12:00
model: admin
category: programs
author_type: human
summary: Issues and renews automatic HTTPS (Let's Encrypt) certificates with a single line of configuration. Simpler to configure compared to nginx.
tags: program, Web server operations, caddy
---

**💬 "caddy Command"**

caddy automatically issues and renews HTTPS (Let's Encrypt) certificates with a single line of configuration for an automatic HTTPS web server. Compared to nginx, its configuration is simpler.

It supports automatic HTTPS certificate issuance and renewal with a single line per domain. It uses two configuration formats: JSON and Caddyfile.

- **Concept**: Supports automatic HTTPS certificate issuance and renewal with a single line per domain.
- **Key Features**: Uses two configuration formats: JSON and Caddyfile.
- **Advantages**: Natively supports HTTP/3 (QUIC).
- **Usage**: Built-in support for static files, reverse proxy, and FastCGI.
## Installation and Download

caddy can be installed via a package manager or an official script.

| Environment | Command |
| --- | --- |
| Ubuntu / Debian | sudo apt install caddy |
| Official Script | curl https://caddyserver.com/api/download?os=linux |
| macOS (brew) | brew install caddy |
| Docker | docker run -p 80:80 -p 443:443 caddy |
| Verification | caddy version |

Verify the installation with `caddy --version`.

## Frequently Used Options

| Option | Description |
| --- | --- |
| caddy run | Run in foreground |
| caddy start | Run in background |
| caddy reload | Reload configuration (zero downtime) |
| caddy validate | Validate configuration syntax |
| sudo systemctl reload caddy | Reload service |

## Three Essential Command Combinations

- `caddy run` — Load Caddyfile and run in foreground
- `caddy validate --config /etc/caddy/Caddyfile` — Validate configuration
- `sudo systemctl reload caddy` — Zero-downtime reload
**💬 "Show an example of using caddy on a real server"**

Here are common situations encountered on a real server, organized step by step.

### Step 1 · Installation Verification

Check if it's installed.

```
caddy version || sudo apt install -y caddy
```

### Step 2 · Configuration Writing

Write the Caddyfile.

```
echo 'example.com {\n    root * /var/www/html\n    file_server\n}' > /etc/caddy/Caddyfile
```

### Step 3 · Start

Start caddy and verify.

```
sudo systemctl restart caddy && curl -sI https://example.com/
```

## Actual Execution Screen

Result of writing the Caddyfile and validating the configuration.

![caddy command execution result](https://games.aidebatehub.com/assets/caddy-demo.png)

Real server in operation

## In Practice, It Is Used Like This

### 1. Migrating from nginx to Caddy

**Situation** — Migrate nginx 443 block to a Caddyfile.

```
echo 'example.com {\n    root * /var/www/html\n    file_server\n    encode gzip\n}' > /etc/caddy/Caddyfile
```

**Result** — Configuration is complete with a single Caddyfile.

**Key Points** — No need for separate certbot cron or additional settings.

### 2. Verifying Automatic HTTPS

**Situation** — Verify automatic certificate issuance.

```
sudo systemctl restart caddy && sleep 5 && curl -sI https://example.com/
```

**Result** — HTTP/2 200 and server: Caddy are visible.

**Key Points** — Automatic HTTPS works in the browser.

## Actual Execution Screen

Result of confirming that automatic HTTPS works after starting caddy.

![caddy command execution result 2](https://games.aidebatehub.com/assets/caddy-demo2.png)

Real server in operation

## Points to Note

- If the site address in the Caddyfile does not specify a port, it defaults to 80/443. Be cautious of port conflicts.
- Automatic HTTPS only works if the domain actually points to the caddy server. Certificate issuance will fail if DNS is not configured.
- When switching from nginx to Caddy, nginx-specific modules (e.g., Lua) may not have alternative implementations.

---
Source (HTML): https://games.aidebatehub.com/programs/linux/webserver/caddy.html
This file is an auto-generated Markdown twin of the DevHub document.