# Kafka Connect Single Message Transformations Reference for Confluent Platform A Single Message Transformation (SMT) modifies individual records as they flow through Connect, eliminating the need for a separate stream-processing application. SMTs process inbound records after a source connector produces them but before they are written to Apache Kafka®. Similarly, they process outbound records before they are delivered to a sink connector. The following table outlines the SMTs available for Kafka Connect and their compatibility with specific connectors. | Transform | Description | |------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | [Cast](cast.md#cast) | Cast fields or the entire key or value to a specific type (for example, to force an integer field to a smaller width). | | [Drop](drop.md#drop) | Drop either a key or a value from a record and set it to null. | | [DropHeaders](dropheaders.md#dropheaders) | Drop one or more headers from each record. | | [EventRouter](eventrouter.md#eventrouter) | Route Debezium outbox events using a regular expression configuration option. | | [ExtractField](extractfield.md#extractfield) | Extract the specified field from a Struct when schema present, or a Map for schemaless data. Any null values are passed through unmodified. | | [ExtractTopic](extracttopic.md#extracttopic) | Replace the record topic with a new topic derived from its key or value. | | [Filter (Apache Kafka)](filter-ak.md#ak-filter) | Drop all records. Designed to be used in conjunction with a [Predicate](filter-ak.md#predicates). | | [Filter (Confluent)](filter-confluent.md#confluent-filter) | Include or drop records that match a configurable `filter.condition`. | | [Flatten](flatten.md#flatten) | Flatten a nested data structure. This generates names for each field by concatenating the field names at each level with a configurable delimiter character. | | [GzipDecompress](gzipdecompress.md#gzipdecompress) | **Not currently available for managed connectors.** Gzip-decompress the entire byteArray key or value input. | | [HeaderFrom](headerfrom.md#headerfrom) | Moves or copies fields in a record key or value into the record’s header. | | [HoistField](hoistfield.md#hoistfield) | Wrap data using the specified field name in a Struct when schema present, or a Map for schemaless data. | | [InsertField](insertfield.md#insertfield) | Insert field using attributes from the record metadata or a configured static value. | | [InsertHeader](insertheader.md#insertheader) | Insert a literal value as a record header. | | [MaskField](maskfield.md#maskfield) | Mask specified fields with a valid null value for the field type. | | [MessageTimestampRouter](messagetimestamprouter.md#messagetimestamprouter) | Update the record’s topic field as a function of the original topic value and the record’s timestamp field. | | [RegexRouter](regexrouter.md#regexrouter) | **Not currently available for managed connectors.** Update the record topic using the configured regular expression and replacement string. | | [ReplaceField (Apache Kafka)](replacefield-ak.md#replacefield) | Filter or rename fields. | | [ReplaceField (Confluent)](replacefield-confluent.md#confluent-replacefield) | Filter or rename nested fields. | | [SetSchemaMetadata](setschemametadata.md#setschemametadata) | Set the schema name, version, or both on the record’s key or value schema. | | [TimescaleDB](timescaledb.md#timescaledb) | **Only available for Debezium PostgreSQL CDC V2 Source connectors.** Consolidate change events from individual TimescaleDB chunk tables into logical hypertable topics and add TimescaleDB metadata to the record headers. | | [TimestampConverter](timestampconverter.md#timestampconverter) | Convert timestamps between different formats such as Unix epoch, strings, and Connect Date and Timestamp types. | | [TimestampRouter](timestamprouter.md#timestamprouter) | Update the record’s topic field as a function of the original topic value and the record timestamp. | | [TimezoneConverter](timezoneconverter.md#timezoneconverter) | **Only available for Oracle XStream CDC Source and managed Debezium connectors.** Convert the timezone of timestamp fields in Debezium change event records to a specified target timezone. | | [TombstoneHandler](tombstonehandler.md#tombstonehandler) | Manage tombstone records. A tombstone record has its entire value field set to null, regardless of whether a value schema is present. | | [ValueToKey](valuetokey.md#valuetokey) | Replace the record key with a new key formed from a subset of fields in the record value. | If the available SMTs do not provide the necessary transformation, you can create your own SMT for Confluent Platform. For more information, see [Create Custom Kafka Connect Single Message Transformations for Confluent Platform](/platform/current/connect/transforms/custom.html).