# Kafka Connect HeaderFrom SMT Usage Reference for Confluent Platform The `HeaderFrom` SMT (`org.apache.kafka.connect.transforms.HeaderFrom`) moves or copies fields in an Apache Kafka® record key or value into the record’s headers. ## Description The `HeaderFrom` SMT exposes record fields as header metadata for routing, filtering, or downstream processing. The `operation` property controls how the source fields are handled after the transfer: * `move` removes the fields from the original key or value. * `copy` retains the fields in the original key or value. Select the transformation type based on where the target fields reside: * Record key: `org.apache.kafka.connect.transforms.HeaderFrom$Key` * Record value: `org.apache.kafka.connect.transforms.HeaderFrom$Value` For related header operations, see the [DropHeaders SMT](dropheaders.md#dropheaders) and the [InsertHeader SMT](insertheader.md#insertheader). ## Properties #### HeaderFrom SMT configuration properties | Name | Description | Type | Default | Valid values | Importance | |-----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------|------------|-------------------|--------------| | `fields` | Specifies a comma-separated list of field names to move or copy into the record header. | List | (required) | Non-empty list | High | | `headers` | Specifies a comma-separated list of header names.

The list must match the `fields` list in count and order. Headers and fields are paired by position: the first header receives the first field, and the second header receives the second field. | List | (required) | Non-empty list | High | | `operation` | Specifies whether to move or copy fields into the record header.

The `move` operation removes the fields from the source record key or value. The `copy` operation retains them. | String | (required) | `move`, `copy` | High | | `replace.null.with.default` | Specifies whether to replace null fields with their defined default
values.

When set to `true`, the default value is applied. Otherwise,
the field remains null. | Boolean | `true` | `true` or `false` | Medium | ## Example: Move fields to record headers The following configuration moves the fields `id` and `ts` from the record’s value into the record’s headers as `record_id` and `event_timestamp`, and removes the fields from the record value. ```json "transforms": "moveFieldsToHeader", "transforms.moveFieldsToHeader.type": "org.apache.kafka.connect.transforms.HeaderFrom$Value", "transforms.moveFieldsToHeader.fields": "id,ts", "transforms.moveFieldsToHeader.headers": "record_id,event_timestamp", "transforms.moveFieldsToHeader.operation": "move" ``` **Before:** * **Record value** ```json { "id": 24, "ts": 1626102708861, "name": "John Smith", "book": "Kafka: The Definitive Guide" } ``` * **Record header** ```json { "source": "RedditSource" } ``` **After:** * **Record value** ```json { "name": "John Smith", "book": "Kafka: The Definitive Guide" } ``` * **Record header** ```json { "source": "RedditSource", "record_id": 24, "event_timestamp": 1626102708861 } ``` #### NOTE Record headers are an ordered list of key-value entries. The JSON objects above are illustrative representations of the header contents. ## Predicates Configure transformations with predicates to ensure they process only records that satisfy a particular condition. You can also use predicates in a transformation chain with the [Kafka Connect Filter (Kafka) SMT Usage Reference for Confluent Platform](filter-ak.md#ak-filter) to conditionally filter specific records. For more information, see [Predicates](filter-ak.md#predicates).