﻿---
title: Append processor
description: Use the Append processor to add a value to an existing array field, or create the field as an array if it doesn’t exist. To use an append processor: Select...
url: https://www.elastic.co/elastic/docs-builder/docs/2542/solutions/observability/streams/management/extract/append
applies_to:
  - Elastic Cloud Serverless: Generally available
  - Elastic Stack: Generally available since 9.2, Preview in 9.1
---

# Append processor
Use the **Append** processor to add a value to an existing array field, or create the field as an array if it doesn’t exist.
To use an append processor:
1. Select **Create** → **Create processor**.
2. Select **Append** from the **Processor** menu.
3. Set **Source Field** to the field you want append values to.
4. Set **Target field** to the values you want to append to the **Source Field**.

This functionality uses the Elasticsearch [append processor](https://docs-v3-preview.elastic.dev/elastic/docs-builder/docs/2542/reference/enrich-processor/append-processor) internally, but you configure it in Streamlang. Streamlang doesn’t always have 1:1 parity with the ingest processor options and behavior. Refer to [Processor limitations and inconsistencies](/elastic/docs-builder/docs/2542/solutions/observability/streams/management/extract#streams-processor-inconsistencies).