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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

<table> <tr> <th>

Module

</th> <th>

Kafka Version

</th> <th>

Java 11

</th> <th>

Java 17

</th> <th>

Java 23

</th> </tr> <tr> <td>

Clients

</td> <td>

4.0.0

</td> <td>

✅

</td> <td>

✅

</td> <td>

✅

</td> </tr> <tr> <td>

Streams

</td> <td>

4.0.0

</td> <td>

✅

</td> <td>

✅

</td> <td>

✅

</td> </tr> <tr> <td>

Connect

</td> <td>

4.0.0

</td> <td>

❌

</td> <td>

✅

</td> <td>

✅

</td> </tr> <tr> <td>

Server

</td> <td>

4.0.0

</td> <td>

❌

</td> <td>

✅

</td> <td>

✅

</td> </tr> </table>

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

Server Compatibility

<table> <tr> <th>

KRaft Cluster Version

</th> <th>

Compatibility 4.0 Server (dynamic voter)

</th> <th>

Compatibility 4.0 Server (static voter)

</th> </tr> <tr> <td>

before 3.2.x

</td> <td>

❌

</td> <td>

❌

</td> </tr> <tr> <td>

3.3.x

</td> <td>

❌

</td> <td>

✅

</td> </tr> <tr> <td>

3.4.x

</td> <td>

❌

</td> <td>

✅

</td> </tr> <tr> <td>

3.5.x

</td> <td>

❌

</td> <td>

✅

</td> </tr> <tr> <td>

3.6.x

</td> <td>

❌

</td> <td>

✅

</td> </tr> <tr> <td>

3.7.x

</td> <td>

❌

</td> <td>

✅

</td> </tr> <tr> <td>

3.8.x

</td> <td>

❌

</td> <td>

✅

</td> </tr> <tr> <td>

3.9.x

</td> <td>

✅

</td> <td>

✅

</td> </tr> <tr> <td>

4.0.x

</td> <td>

✅

</td> <td>

✅

</td> </tr> </table>

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

Client/Broker Forward Compatibility

<table> <tr> <th>Kafka Version</th> <th>Module</th> <th>Compatibility with Kafka 4.0</th> <th>Key Differences/Limitations</th> </tr> <tr> <td rowspan="3">0.x, 1.x, 2.0</td> <td>Client</td> <td>❌ Not Compatible</td> <td>

Pre-0.10.x protocols are fully removed in Kafka 4.0 (KIP-896).

</td> </tr> <tr> <td>Streams</td> <td>❌ Not Compatible</td> <td>

Pre-0.10.x protocols are fully removed in Kafka 4.0 (KIP-896).</td>

</tr> <tr> <td>Connect</td> <td>❌ Not Compatible</td> <td>

Pre-0.10.x protocols are fully removed in Kafka 4.0 (KIP-896).</td>

</tr> <tr> <td rowspan="3">2.1 ~ 2.8</td> <td>Client</td> <td>⚠️ Partially Compatible</td> <td>

More details in the Consumer, Producer, and Admin Client section.</td>

</tr> <tr> <td>Streams</td> <td>⚠️ Limited Compatibility</td> <td>

More details in the Kafka Streams section.</td>

</tr> <tr> <td>Connect</td> <td>⚠️ Limited Compatibility</td> <td>

More details in the Connect section.</td>

</tr> <tr> <td rowspan="3">3.x</td> <td>Client</td> <td>✅ Fully Compatible</td> <td>—</td> </tr> <tr> <td>Streams</td> <td>✅ Fully Compatible</td> <td>—</td> </tr> <tr> <td>Connect</td> <td>✅ Fully Compatible</td> <td>—</td> </tr> </table>

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.