> ## 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.

# caddy adapt

> Convert a config file to Caddy's native JSON format

The `caddy adapt` command adapts a configuration to Caddy's native JSON format and outputs the result.

## Usage

```bash theme={null}
caddy adapt --config <path> [flags]
```

## Description

Adapts a configuration to Caddy's native JSON format and writes the output to stdout, along with any warnings to stderr.

This is useful for:

* **Previewing** how your Caddyfile will be converted to JSON
* **Debugging** config adapter behavior
* **Validating** your config syntax
* **Learning** Caddy's JSON structure
* **Generating** JSON configs from other formats

## Flags

<ParamField path="--config" type="string" required>
  Configuration file to adapt (required).

  Use `-` to read from stdin instead of a file.
</ParamField>

<ParamField path="--adapter" type="string" default="caddyfile">
  Name of config adapter to use.

  Default: `caddyfile`

  Available adapters depend on what's compiled in. Common ones:

  * `caddyfile` - Caddyfile format
  * `yaml` - YAML format (if installed)
</ParamField>

<ParamField path="--pretty" type="boolean" default="false">
  Format the output with indentation for human readability.

  Without this flag, output is compact JSON on a single line.
</ParamField>

<ParamField path="--validate" type="boolean" default="false">
  Validate the adapted config.

  If the config is invalid, an error will be printed to stderr and a non-zero exit status will be returned.
</ParamField>

<ParamField path="--envfile" type="string[]" default="[]">
  Environment file(s) to load in KEY=VALUE format.

  Useful if your config references environment variables.
</ParamField>

## Examples

### Basic adaptation

```bash theme={null}
caddy adapt --config Caddyfile
```

Outputs compact JSON to stdout.

### Pretty-printed output

```bash theme={null}
caddy adapt --config Caddyfile --pretty
```

Outputs formatted JSON:

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

### Adapt and validate

```bash theme={null}
caddy adapt --config Caddyfile --validate
```

This ensures the adapted JSON config is valid before using it.

### Adapt from stdin

```bash theme={null}
cat Caddyfile | caddy adapt --config - --adapter caddyfile --pretty
```

### Save to file

```bash theme={null}
caddy adapt --config Caddyfile --pretty > config.json
```

### Adapt with environment variables

```bash theme={null}
caddy adapt --config Caddyfile --envfile .env --pretty
```

If your Caddyfile uses `{env.VARIABLE}`, the environment file will be loaded.

### Adapt YAML config

```bash theme={null}
caddy adapt --config caddy.yaml --adapter yaml --pretty
```

## Output

The adapted JSON is written to **stdout**, and any warnings are written to **stderr**.

<CodeGroup>
  ```bash Input Caddyfile theme={null}
  example.com {
      reverse_proxy localhost:8080
  }
  ```

  ```json Output JSON (--pretty) theme={null}
  {
    "apps": {
      "http": {
        "servers": {
          "srv0": {
            "listen": [
              ":443"
            ],
            "routes": [
              {
                "match": [
                  {
                    "host": [
                      "example.com"
                    ]
                  }
                ],
                "handle": [
                  {
                    "handler": "subroute",
                    "routes": [
                      {
                        "handle": [
                          {
                            "handler": "reverse_proxy",
                            "upstreams": [
                              {
                                "dial": "localhost:8080"
                              }
                            ]
                          }
                        ]
                      }
                    ]
                  }
                ],
                "terminal": true
              }
            ]
          }
        }
      }
    }
  }
  ```
</CodeGroup>

## Exit Codes

* `0` - Success
* `1` - Failed (adaptation error or validation error)

## Warnings

Warnings are printed to stderr with file location:

```
Caddyfile:10: some_directive: this is a warning message
```

Warnings don't cause the command to fail, but you should review them.

## Validation

With the `--validate` flag, the adapted config is:

1. **Unmarshaled** into Go structs
2. **Validated** by calling `Validate()` on all modules
3. **Checked** for errors

If validation fails:

```
Error: validation: field 'required_field' is required
```

<Note>
  Validation catches many errors but not all. Some errors only appear at runtime when the config is actually loaded.
</Note>

## Use Cases

### 1. Preview before applying

```bash theme={null}
# Preview the JSON
caddy adapt --config Caddyfile --pretty

# If it looks good, apply it
caddy reload --config Caddyfile
```

### 2. Generate production JSON

```bash theme={null}
# Generate and save
caddy adapt --config Caddyfile --pretty --validate > /etc/caddy/config.json

# Use in production
caddy run --config /etc/caddy/config.json
```

### 3. Debug config issues

```bash theme={null}
caddy adapt --config Caddyfile --pretty --validate 2>&1 | less
```

### 4. Learn JSON structure

Write a simple Caddyfile feature, then adapt it to see the JSON equivalent:

```bash theme={null}
echo 'localhost { respond "Hello" }' | caddy adapt --config - --pretty
```

### 5. CI/CD validation

```bash theme={null}
#!/bin/bash
if caddy adapt --config Caddyfile --validate; then
    echo "Config is valid"
else
    echo "Config is invalid"
    exit 1
fi
```

## Related Commands

* [`caddy validate`](/cli/validate) - Validate without adapting (if already JSON)
* [`caddy reload`](/cli/reload) - Apply a config to running Caddy
* [`caddy run`](/cli/run) - Start Caddy with a config