Compatibility

With the release of Kafka 4.0, significant changes have been introduced that impact compatibility across various components. To assist users in planning upgrades and ensuring seamless interoperability, a comprehensive compatibility matrix has been prepared.

JDK Compatibility Across Kafka Versions

Module	Kafka Version	Java 11	Java 17	Java 23
Clients	4.0.0	✅	✅	✅
Streams	4.0.0	✅	✅	✅
Connect	4.0.0	❌	✅	✅
Server	4.0.0	❌	✅	✅

Note: Java 8 is removed in Kafka 4.0 and is no longer supported.

Server Compatibility

KRaft Cluster Version	Compatibility 4.0 Server (dynamic voter)	Compatibility 4.0 Server (static voter)
before 3.2.x	❌	❌
3.3.x	❌	✅
3.4.x	❌	✅
3.5.x	❌	✅
3.6.x	❌	✅
3.7.x	❌	✅
3.8.x	❌	✅
3.9.x	✅	✅
4.0.x	✅	✅

Note: Can’t upgrade server from static voter to dynamic voter, see KAFKA-16538.

Client/Broker Forward Compatibility

Kafka Version	Module	Compatibility with Kafka 4.0	Key Differences/Limitations
0.x, 1.x, 2.0	Client	❌ Not Compatible	Pre-0.10.x protocols are fully removed in Kafka 4.0 (KIP-896).
	Streams	❌ Not Compatible	Pre-0.10.x protocols are fully removed in Kafka 4.0 (KIP-896).
	Connect	❌ Not Compatible	Pre-0.10.x protocols are fully removed in Kafka 4.0 (KIP-896).
2.1 ~ 2.8	Client	⚠️ Partially Compatible	More details in the Consumer, Producer, and Admin Client section.
	Streams	⚠️ Limited Compatibility	More details in the Kafka Streams section.
	Connect	⚠️ Limited Compatibility	More details in the Connect section.
3.x	Client	✅ Fully Compatible
	Streams	✅ Fully Compatible
	Connect	✅ Fully Compatible

Note: Starting with Kafka 4.0, the --zookeeper option in AdminClient commands has been removed. Users must use the --bootstrap-server option to interact with the Kafka cluster. This change aligns with the transition to KRaft mode.