Browse Kafka Schema Registry Subjects and Versions
Kafma gives you one place to browse the subjects registered on a connection's Schema Registry. Open a subject in a full-width drawer to inspect its versions, schema IDs, fields, and compatibility.
What is a Kafka Schema Registry?
Kafka stores message keys and values as bytes. A Schema Registry stores the structure used to serialize and deserialize those bytes, allowing producers and consumers to agree on a format without placing the full schema in every record.
Three identifiers matter:
| Term | Meaning |
|---|---|
| Subject | A named history of related schema versions |
| Version | A subject-local number assigned when a schema is registered |
| Schema ID | A registry-wide identifier for the registered schema |
Versions are scoped to a subject. A schema ID is unique across the registry, but it is not exclusive to one subject. If two subjects register the same schema definition, Schema Registry returns the existing ID instead of creating a new one, so both subjects use the same ID.
For records using the Confluent wire format, the producer writes the schema ID with the payload. A consumer uses that ID to retrieve the matching schema and decode the record.
Browse Schema Registry subjects
The Schema Registry list shows each active subject with:
- Its Avro, JSON Schema, or Protobuf format.
- The latest active version and its schema ID.
- The number of active versions.
Filter by subject name or format to narrow a large registry. Refresh the list when another application registers a schema, or pin a subject to the Watchlist for faster access from Home.
The list reflects active subjects and versions returned by the registry. Permanently deleted versions do not remain in this history.
Inspect schema versions and fields
Select a subject to open its details in a full-width drawer over the Schema Registry list. Close the drawer to return to the list. The summary shows the registry mode, latest version, number of active versions, schema format, field count, and effective compatibility level.
The version selector starts on the latest version and lets you inspect any active version. The Schema tab places the registered source beside its parsed fields. When a version declares schema references, expand References to see the referenced subject and version.
The remaining tabs answer focused questions:
- Mock generates a sample payload from the selected version.
- Lab validates a JSON payload against that version.
- Diff compares two active versions.
See Avro Schema Validator and Mock Data Generator for the Mock and Lab workflows.
Set Schema Registry compatibility
The compatibility setting decides whether the registry accepts a new schema version. Use the control at the top of the page to set the global default. Subjects that inherit this setting update with it.
A subject can override the global level. Open its drawer and use the edit icon on the Compatibility card to choose an override, or reset the subject to inherit the global setting again. A global change does not replace a subject override.
Compatibility and registry mode are separate. Compatibility evaluates a schema change; mode controls whether the registry accepts writes at all. Kafma disables write actions on read-only connections and in non-writable registry modes.
See Register Kafka Schemas and Publish New Versions for the compatibility levels and their effect on schema changes.
Delete a Schema Registry subject
Deleting a subject is permanent. Kafma first soft-deletes it, then permanently deletes all subject-version registrations. After Schema Registry confirms the deletion, Kafma removes the subject from the list and Watchlist.
This operation does not delete a Kafka topic or its messages. Before confirming, check whether producers, consumers, or other schemas still depend on the subject. Deletion is unavailable on read-only connections and in non-writable registry modes.