---
title: "declare | Grafana Cloud documentation"
description: "Learn about the declare configuration block"
---

# `declare`

`declare` is an optional configuration block used to define a new [custom component](/docs/alloy/latest/get-started/custom_components). `declare` blocks must be given a label that determines the name of the custom component.

## Usage

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
declare "<COMPONENT_NAME>" {
    <COMPONENT_DEFINITION>
}
```

## Arguments

The `declare` block has no predefined schema for its arguments. The body of the `declare` block is used as the component definition. The body can contain the following:

- [`argument`](/docs/grafana-cloud/send-data/alloy/reference/config-blocks/argument) blocks
- [`export`](/docs/grafana-cloud/send-data/alloy/reference/config-blocks/export) blocks
- [`declare`](/docs/grafana-cloud/send-data/alloy/reference/config-blocks/declare) blocks
- [`import`](/docs/grafana-cloud/send-data/alloy/get-started/modules/#import-modules) blocks
- Component definitions (either built-in or custom components)

The `declare` block may not contain any configuration blocks that aren’t listed above.

## Exported fields

The `declare` block has no predefined schema for its exports. The fields exported by the `declare` block are determined by the [export blocks](/docs/grafana-cloud/send-data/alloy/reference/config-blocks/export) found in its definition.

## Example

This example creates and uses a custom component that self-collects process metrics and forwards them to an argument specified by the user of the custom component:

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
declare "self_collect" {
  argument "metrics_output" {
    optional = false
    comment  = "Where to send collected metrics."
  }

  prometheus.scrape "selfmonitor" {
    targets = [{
      __address__ = "127.0.0.1:12345",
    }]

    forward_to = [argument.metrics_output.value]
  }
}

self_collect "example" {
  metrics_output = prometheus.remote_write.example.receiver
}

prometheus.remote_write "example" {
  endpoint {
    url = <REMOTE_WRITE_URL>
  }
}
```