# Kafka Connect InsertField SMT Usage Reference for Confluent Platform The `InsertField` SMT (`org.apache.kafka.connect.transforms.InsertField`) adds fields to an Apache Kafka® record key or value, using attributes from the record metadata or a configured static value. ## Description Use `InsertField` to add metadata fields (such as topic, partition, offset, or timestamp) or a static field with a fixed value to each record. Suffix a field name with `!` to make it required, or `?` to keep it optional. Use the concrete transformation type designed for the record key (`org.apache.kafka.connect.transforms.InsertField$Key`) or value (`org.apache.kafka.connect.transforms.InsertField$Value`). #### NOTE When you use `InsertField` with a source connector, the SMT inserts `null` for the Kafka record metadata fields `timestamp.field` and `partition.field`. This is because the SMT runs before the record reaches the Kafka topic, where Kafka assigns these metadata values. To insert non-null metadata-based fields, use `InsertField` with a sink connector. For source connectors, use `static.field` and `static.value` to insert fixed values instead. ## Properties | Name | Description | Type | Default | Valid values | Importance | |-----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------|-----------|----------------|--------------| | `offset.field` | Field name for Kafka offset. This is only applicable to sink connectors. Suffix with `!` to make this a required field, or `?` to keep it optional (the default). | string | null | | medium | | `partition.field` | Field name for Kafka partition. Suffix with `!` to make this a required field, or `?` to keep it optional (the default). | string | null | | medium | | `replace.null.with.default` | Whether to replace fields that have a default value and are null with the default value. When `true`, the default value is used; otherwise, `null` is used. | boolean | true | | medium | | `static.field` | Field name for static data field. Suffix with `!` to make this a required field, or `?` to keep it optional (the default). | string | null | | medium | | `static.value` | The static value to insert when a field name is configured. | string | null | | medium | | `timestamp.field` | Field name for record timestamp. Suffix with `!` to make this a required field, or `?` to keep it optional (the default). | string | null | | medium | | `topic.field` | Field name for Kafka topic. Suffix with `!` to make this a required field, or `?` to keep it optional (the default). | string | null | | medium | ## Example This configuration snippet shows how to use `InsertField` to insert a static field labeled `MessageSource` using a static value of `Kafka Connect Framework`. ```json "transforms": "InsertField", "transforms.InsertField.type": "org.apache.kafka.connect.transforms.InsertField$Value", "transforms.InsertField.static.field": "MessageSource", "transforms.InsertField.static.value": "Kafka Connect Framework" ``` Before: `{"author": "Philip K. Dick", "character": "Palmer Eldritch"}` After: `{"author": "Philip K. Dick", "character": "Palmer Eldritch", "MessageSource": "Kafka Connect Framework"}` ## 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).