---
title: Join processor
description: Joins each element of an array into a single string using a separator character between each element. Throws an error when the field is not an array. 
url: https://www.elastic.co/elastic/docs-builder/docs/3028/reference/enrich-processor/join-processor
products:
  - Elasticsearch
---

# Join processor
Joins each element of an array into a single string using a separator character between each element. Throws an error when the field is not an array.


| Name             | Required | Default | Description                                                                                                                                                                                                                    |
|------------------|----------|---------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `field`          | yes      | -       | Field containing array values to join                                                                                                                                                                                          |
| `separator`      | yes      | -       | The separator character                                                                                                                                                                                                        |
| `target_field`   | no       | `field` | The field to assign the joined value to, by default `field` is updated in-place                                                                                                                                                |
| `description`    | no       | -       | Description of the processor. Useful for describing the purpose of the processor or its configuration.                                                                                                                         |
| `if`             | no       | -       | Conditionally execute the processor. See [Conditionally run a processor](https://docs-v3-preview.elastic.dev/elastic/docs-builder/docs/3028/manage-data/ingest/transform-enrich/ingest-pipelines#conditionally-run-processor). |
| `ignore_failure` | no       | `false` | Ignore failures for the processor. See [Handling pipeline failures](https://docs-v3-preview.elastic.dev/elastic/docs-builder/docs/3028/manage-data/ingest/transform-enrich/ingest-pipelines#handling-pipeline-failures).       |
| `on_failure`     | no       | -       | Handle failures for the processor. See [Handling pipeline failures](https://docs-v3-preview.elastic.dev/elastic/docs-builder/docs/3028/manage-data/ingest/transform-enrich/ingest-pipelines#handling-pipeline-failures).       |
| `tag`            | no       | -       | Identifier for the processor. Useful for debugging and metrics.                                                                                                                                                                |

```js
{
  "join": {
    "field": "joined_array_field",
    "separator": "-"
  }
}
```