---
title: Concat processor
description: The Concat processor concatenates a mix of field values and literal strings into a single field. To concatenate values: Select Create → Create processor.Select...
url: https://www.elastic.co/elastic/docs-builder/docs/3016/solutions/observability/streams/management/extract/concat
products:
  - Elastic Cloud Enterprise
  - Elastic Cloud Hosted
  - Elastic Cloud Serverless
  - Elastic Cloud on Kubernetes
  - Elastic Observability
  - Elastic Stack
  - Elasticsearch
  - Kibana
applies_to:
  - Elastic Cloud Serverless: Generally available
  - Elastic Stack: Planned
---

# Concat processor
The **Concat** processor concatenates a mix of field values and literal strings into a single field.
To concatenate values:
1. Select **Create** → **Create processor**.
2. Select **Concat** from the **Processor** menu.
3. Set the items to concatenate. Each item is either a field reference or a literal string value.
4. Set the **Target field** where the concatenated result is stored.


## YAML reference

In [YAML mode](/elastic/docs-builder/docs/3016/solutions/observability/streams/management/extract#streams-editing-yaml-mode), configure the concat processor using the following parameters. For the complete Streamlang syntax, refer to the [Streamlang reference](https://www.elastic.co/elastic/docs-builder/docs/3016/solutions/observability/streams/management/streamlang).

| Parameter        | Type    | Required | Description                                                                                                                     |
|------------------|---------|----------|---------------------------------------------------------------------------------------------------------------------------------|
| `from`           | array   | Yes      | Items to concatenate. Each item is either `{ type: "field", value: "<field_name>" }` or `{ type: "literal", value: "<text>" }`. |
| `to`             | string  | Yes      | Target field.                                                                                                                   |
| `ignore_missing` | boolean | No       | When `true`, skip this processor if any referenced field is missing.                                                            |

```yaml
- action: concat
  from:
    - type: literal
      value: "User: "
    - type: field
      value: attributes.username
    - type: literal
      value: " (ID: "
    - type: field
      value: attributes.user_id
    - type: literal
      value: ")"
  to: attributes.user_summary
```