> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/caddyserver/caddy/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction to Caddy

> A modern, extensible web server platform with automatic HTTPS that serves every site securely by default

# Every site on HTTPS

Caddy is an extensible server platform that uses TLS by default. Built with Go, it offers higher memory safety guarantees than other servers and runs anywhere with no external dependencies.

<CardGroup cols={2}>
  <Card title="Quick Start" icon="rocket" href="/quickstart">
    Get up and running with Caddy in minutes
  </Card>

  <Card title="Installation" icon="download" href="/install">
    Download and install Caddy on your platform
  </Card>

  <Card title="Configuration" icon="sliders" href="/config/caddyfile">
    Learn the Caddyfile syntax for easy configuration
  </Card>

  <Card title="API Reference" icon="code" href="/guides/api">
    Explore Caddy's powerful JSON API
  </Card>
</CardGroup>

## Key Features

### Automatic HTTPS by Default

Caddy automatically obtains and renews TLS certificates for your sites, with no configuration required.

<CardGroup cols={2}>
  <Card title="Zero Config TLS" icon="shield-check">
    Caddy obtains certificates from ZeroSSL and Let's Encrypt automatically. No manual certificate management needed.
  </Card>

  <Card title="Fully-Managed Local CA" icon="building">
    Internal names and IPs get certificates from a local CA that Caddy manages for you.
  </Card>

  <Card title="Cluster Coordination" icon="network-wired">
    Multiple Caddy instances can coordinate certificate management in a cluster.
  </Card>

  <Card title="ECH Support" icon="lock">
    Encrypted ClientHello (ECH) support for enhanced privacy.
  </Card>
</CardGroup>

### Production-Ready at Scale

Caddy has served **trillions of requests** and managed **millions of TLS certificates** in production environments.

<Note>
  Caddy scales to hundreds of thousands of sites as proven in production deployments worldwide.
</Note>

### Modern Protocol Support

* **HTTP/1.1, HTTP/2, and HTTP/3** all supported by default
* No configuration needed to enable modern protocols
* Automatic protocol negotiation

### Highly Extensible Architecture

Caddy's modular architecture allows it to do anything without bloat:

```go theme={null}
// Example: Caddy apps are just Go programs implemented as modules
type App interface {
    Start() error
    Stop() error
}
```

<CodeGroup>
  ```go Main Entry Point theme={null}
  // From cmd/main.go
  func Main() {
      if len(os.Args) == 0 {
          fmt.Printf("[FATAL] no arguments provided by OS; args[0] must be command\n")
          os.Exit(caddy.ExitCodeFailedStartup)
      }

      if err := defaultFactory.Build().Execute(); err != nil {
          var exitError *exitError
          if errors.As(err, &exitError) {
              os.Exit(exitError.ExitCode)
          }
          os.Exit(1)
      }
  }
  ```

  ```go HTTP Handler Interface theme={null}
  // From modules/caddyhttp/caddyhttp.go
  // Handler is like http.Handler except ServeHTTP may return an error.
  type Handler interface {
      ServeHTTP(http.ResponseWriter, *http.Request) error
  }

  // MiddlewareHandler chains handlers together
  type MiddlewareHandler interface {
      ServeHTTP(http.ResponseWriter, *http.Request, Handler) error
  }
  ```
</CodeGroup>

## Configuration Approaches

Caddy is unique in offering multiple ways to configure the same server:

<Steps>
  <Step title="Caddyfile (Recommended for most)">
    The Caddyfile is Caddy's native configuration format - simple, human-readable, and powerful.

    ```caddyfile theme={null}
    example.com {
        reverse_proxy localhost:9000
    }
    ```
  </Step>

  <Step title="JSON (Native format)">
    JSON is Caddy's native config language. The Caddyfile and other formats are adapted to JSON.

    ```json theme={null}
    {
      "apps": {
        "http": {
          "servers": {
            "srv0": {
              "listen": [": 443"],
              "routes": [...]
            }
          }
        }
      }
    }
    ```
  </Step>

  <Step title="JSON API (Dynamic configuration)">
    Caddy exposes a RESTful JSON API for dynamic, runtime configuration changes with zero downtime.

    ```bash theme={null}
    curl -X POST http://localhost:2019/load \
      -H "Content-Type: application/json" \
      -d @caddy.json
    ```
  </Step>

  <Step title="Config Adapters">
    Use config adapters to convert other formats (YAML, TOML, NGINX config) into Caddy JSON.
  </Step>
</Steps>

## Why Caddy?

### Stays Up When Others Go Down

Caddy continues serving even when other servers would crash due to TLS, OCSP, or certificate-related issues.

### No External Dependencies

Caddy runs anywhere with no external dependencies - not even libc. Just download and run.

### Memory Safety

Written in Go, a language with higher memory safety guarantees than C/C++ servers.

### Actually Fun to Use

From the README:

> Actually **fun to use**

<Warning>
  The name "Caddy" is trademarked. Please call it "Caddy" or "the Caddy web server", not "Caddy Server" or "CaddyServer".
</Warning>

## Architecture Overview

Caddy is built on a powerful plugin system:

```go theme={null}
// From caddy.go - Config structure
type Config struct {
    Admin   *AdminConfig `json:"admin,omitempty"`
    Logging *Logging     `json:"logging,omitempty"`
    
    // StorageRaw is a storage module for assets like TLS certificates
    StorageRaw json.RawMessage `json:"storage,omitempty"`
    
    // AppsRaw are the apps that Caddy will load and run
    AppsRaw ModuleMap `json:"apps,omitempty"`
}
```

### Core Apps

Two apps ship standard with Caddy:

1. **`tls`** - Provides TLS facilities including certificate loading, management, and client auth
2. **`http`** - Full-featured HTTP server with reverse proxy, file server, and more

## Project Information

<Note>
  Caddy was created by **Matthew Holt** in 2014 while studying computer science at Brigham Young University. It became the first web server to use HTTPS automatically and by default.
</Note>

### Open Source & Community

* **License**: Apache 2.0
* **Language**: Go 1.25.0 or newer required
* **Community**: Active forum at [caddy.community](https://caddy.community)
* **Sponsorship**: Caddy is a project of [ZeroSSL](https://zerossl.com), an HID Global company

### Powered by CertMagic

Caddy's automatic HTTPS is powered by [CertMagic](https://github.com/caddyserver/certmagic), an open-source library that handles all the complexity of certificate management.

## Next Steps

<CardGroup cols={2}>
  <Card title="Get Started" icon="play" href="/quickstart">
    Follow our quick start guide to serve your first site
  </Card>

  <Card title="Install Caddy" icon="download" href="/install">
    Choose your installation method and platform
  </Card>

  <Card title="Learn Caddyfile" icon="book" href="/config/caddyfile">
    Master Caddy's configuration syntax
  </Card>

  <Card title="Explore Modules" icon="puzzle-piece" href="/modules/http/handlers">
    Discover available modules and handlers
  </Card>
</CardGroup>