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

# Flatten Fields Processor

> Recursively collapse nested JSON objects into a single level, joining parent and child keys with a configurable delimiter.

## Description

This processor recursively reduces the level of a set of objects and appends the prior level to the keys of each.

## Use

The flatten processor is useful when you need all nested fields of a JSON object to be moved to a single level. This can be beneficial when integrating with a system that can't handle complex or nested data.

## Configuration

There are two options for configuring this processor.

| **Option** | **Description** | **Example** |
| - | - | - |
| **Fields** | The field or fields to flatten. | `.foo` |
| **Flatten Options** | Specify the delimiter to use for combining field names with the flattened data. | \_ |

## Example

### Before

```json theme={null}
{
  "foo": {
    "bar": {
      "baz": 1,
      "qux": "quux"
    },
    "core": [
      1,
      2,
      3
    ]
  }
}

```

### Flatten Options

| Option | Value |
| - | - |
| **Field** | .`foo` |
| **Delimiter** | \_ |

```json theme={null}
{
  "foo_bar_baz": 1,
  "foo_bar_qux": "quux",
  "foo_core": [
    1,
    2,
    3
  ]
}

```