docs/documentation/compatibility.html

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<div class="content">
    <div class="p-compatibility">
        <h1>Compatibility</h1>
        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.
        <h2 class="anchor-heading">JDK Compatibility Across Kafka Versions</h2>
        <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>
        <p><strong>Note: Java 8 is removed in Kafka 4.0 and is no longer supported.</strong></p>

        <h2 class="anchor-heading">Server Compatibility</h2>
        <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>
        <p><strong>Note: Can’t upgrade server from static voter to dynamic
            voter, see <a href="https://issues.apache.org/jira/browse/KAFKA-16538">KAFKA-16538</a>.</strong></p>

        <h4>Client/Broker Forward Compatibility</h4>
        <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 (<a
                        href="https://cwiki.apache.org/confluence/x/K5sODg">KIP-896</a>).
                </td>
            </tr>
            <tr>
                <td>Streams</td>
                <td>❌ Not Compatible</td>
                <td>Pre-0.10.x protocols are fully removed in Kafka 4.0 (<a
                        href="https://cwiki.apache.org/confluence/x/K5sODg">KIP-896</a>).
                </td>
            </tr>
            <tr>
                <td>Connect</td>
                <td>❌ Not Compatible</td>
                <td>Pre-0.10.x protocols are fully removed in Kafka 4.0 (<a
                        href="https://cwiki.apache.org/confluence/x/K5sODg">KIP-896</a>).
                </td>
            </tr>
            <tr>
                <td rowspan="3">2.1 ~ 2.8</td>
                <td>Client</td>
                <td>⚠️ Partially Compatible</td>
                <td>
                    More details in the <a href="/40/documentation.html#upgrade_400_notable_consumer">Consumer</a>, 
                    <a href="/40/documentation.html#upgrade_400_notable_producer">Producer</a>, and
                    <a href="/40/documentation.html#upgrade_400_notable_admin_client">Admin Client</a> section.
                </td>
            </tr>
            <tr>
                <td>Streams</td>
                <td>⚠️ Limited Compatibility</td>
                <td>
                    More details in the <a href="/40/documentation.html#upgrade_400_notable_kafka_streams">Kafka Streams</a> section.
                </td>
            </tr>
            <tr>
                <td>Connect</td>
                <td>⚠️ Limited Compatibility</td>
                <td>
                    More details in the <a href="/40/documentation.html#upgrade_400_notable_connect">Connect</a> 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>
        <p>
            Note: Starting with Kafka 4.0, the <code>--zookeeper</code> option in AdminClient commands has been removed. Users must
            use the <code>--bootstrap-server</code> option to interact with the Kafka cluster. This change aligns with the transition
            to KRaft mode.
        </p>

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