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

# Append request headers

> Append a header to the request as a key value pair.

export const FormField = ({property, label, required = false, diType, uiPatterns, children}) => {
  const patterns = Array.isArray(uiPatterns) ? uiPatterns : uiPatterns ? [uiPatterns] : [];
  return <div style={{
    margin: '1.5rem 0'
  }}>
      <div style={{
    display: 'flex',
    alignItems: 'baseline',
    flexWrap: 'wrap',
    gap: '0.5rem',
    marginBottom: '0.25rem'
  }}>
        <strong>{label}</strong>
        <span style={{
    fontSize: '0.7rem',
    fontWeight: 600,
    textTransform: 'uppercase',
    letterSpacing: '0.04em',
    color: required ? '#6241f5' : '#6b7280'
  }}>
          {required ? 'Required' : 'Optional'}
        </span>
      </div>

      <div>{children}</div>

      {diType || patterns.length > 0 ? <p style={{
    fontSize: '0.85rem',
    color: '#6b7280',
    marginBottom: 0
  }}>
          {diType ? <>
              See the <a href={`/references/${diType}`}>{diType}</a> reference.{' '}
            </> : null}
          {patterns.length > 0 ? <>
              Accepts a <a href={`/documentation/placeholders-and-patterns/patterns#${patterns[0]}`}>pattern</a>.
            </> : null}
        </p> : null}
    </div>;
};

Adds one or more headers to every request the connection sends. This plugin appends to whatever headers are already on the request, so if a header with the same name is already present, your value is added alongside it rather than replacing it. Use this when an API expects an extra header on each call, such as a tracking tag or an additional content negotiation hint, and you want to keep any value the request already carries.

This documentation describes: [Schema](/schemas/http-client-plugin-configurator/header-append)

## Fields

### Headers

<FormField property="headers" label="Headers">
  The headers to add to each request, entered as name and value pairs. Add a row for every header you want to append. Because these are appended, an existing header of the same name is kept and your value is added to it. To overwrite instead, use the Set request headers plugin.
</FormField>

## Sample data

This plugin adds fixed headers to outgoing requests rather than transforming entity data, so there is no before/after to show. The example below adds an `X-Source` header and an extra `Accept` value to every request the connection makes.

| Field   | Value                                                |
| ------- | ---------------------------------------------------- |
| Headers | `X-Source` = `alumio`, `Accept` = `application/json` |

```json Configuration theme={null}
{
  "prototype": "header-append",
  "parameters": {
    "headers": {
      "X-Source": "alumio",
      "Accept": "application/json"
    }
  }
}
```