# Processing

This section covers Benthos processors for data transformation and message handling. Processors allow you to modify, filter, and enrich messages as they flow through your data pipelines.

## Available Processors

* [**Tag Processor**](https://docs.umh.app/benthos-umh/processing/tag-processor) - Optimized for processing tags and time series data, converting them to the UMH data model within the `_historian` data contract. Provides automatic message formatting, metadata generation, and structured processing stages.
* [**Classic to Core Processor**](https://docs.umh.app/benthos-umh/processing/classic-to-core-processor) - Converts UMH Historian Data Contract format messages into Core format, following the "one tag, one message, one topic" principle.
* [**Downsampler**](https://docs.umh.app/benthos-umh/processing/downsampler) - Reduces time-series data volume by filtering out insignificant changes using configurable algorithms. Integrates with UMH data pipelines to compress historian data while preserving significant trends.
* [**Topic Browser**](https://docs.umh.app/benthos-umh/processing/topic-browser) - **\[Internal]** Transforms UMH messages into structured data for the Topic Browser interface. Extracts hierarchical topic information and event data to enable real-time topic exploration, metadata search, and debugging in the Management Console.
* [**Stream Processor**](https://docs.umh.app/benthos-umh/processing/stream-processor) - Collects timeseries data from multiple UNS sources and generates transformed messages using JavaScript expressions. Implements dependency-based evaluation where static mappings are evaluated on every message while dynamic mappings only evaluate when their dependencies are received.
* [**Node-RED JavaScript Processor**](https://docs.umh.app/benthos-umh/processing/node-red-javascript-processor) - Provides full control over payload and metadata through custom JavaScript code. Use this processor when you need complex transformations, conditional logic, or custom processing beyond standard tag handling.
* [**More Processors**](https://docs.redpanda.com/redpanda-connect/components/processors/about/) - Additional built-in processors available in Benthos/Redpanda Connect for various data processing needs.

## Which Processor to Choose?

* Use **Tag Processor** when working with structured time series data that needs to conform to the UMH data model
* Use **Classic to Core Processor** when migrating from legacy UMH Historian Data Contract format to modern Core format
* Use **Downsampler** after tag\_processor to reduce data volume while preserving important changes in time-series data
* Use **Topic Browser** (internal) when implementing systems that need to consume and display UMH topic hierarchies and event streams
* Use **Stream Processor** when you need to combine data from multiple UNS sources with state management, perform complex JavaScript transformations, and generate new UMH topics based on a model/version data contract
* Use **Node-RED JavaScript Processor** when you need maximum flexibility and custom processing logic
* Explore the **additional processors** for specific use cases like JSON manipulation, HTTP requests, caching, and more