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Karapace
Helsinki, Finland
What it is
Karapace is a free, open-source implementation of the Kafka Schema Registry and Kafka REST Proxy. Its registry stores schemas in one place, keeps version histories and checks compatibility between versions. Supported formats are Avro, JSON Schema and Protobuf. The REST Proxy provides HTTP APIs for producing and consuming Kafka events and handling administrative tasks. Karapace implements the Confluent Schema Registry API and REST Proxy API versions 1 and 2, with version 2 as the default.
A leader-and-replica design supports high availability and load balancing across instances. For monitoring, Karapace exposes Prometheus-native metrics and integrates with OpenTelemetry for traces and metrics; Sentry error reporting can also be enabled. Registry authentication supports HTTP basic authentication and OAuth2/OIDC bearer-token validation. The REST Proxy forwards OAuth2 tokens to Kafka and the registry rather than validating them. Karapace is self-hosted, requires Python 3.12 or newer, and can be installed from Docker images or source. Its default Docker setup exposes the registry on port 8081 and REST Proxy on port 8082.
For and against
For
- Free and open source.
- Supports Avro, JSON Schema and Protobuf.
- Tracks schema versions and checks compatibility.
- Provides Prometheus metrics and OpenTelemetry integration.
- Offers HTTP basic and OAuth2/OIDC registry authentication.
Against
- Requires Python 3.12 or newer.
- Requires self-hosted installation.
- JSON Schema references are not supported.
- Normalization support is limited to Protobuf.
The verdict
Karapace combines schema management and a Kafka REST interface, with monitoring and authentication options. Its self-hosted setup and specific schema limitations are important considerations.
Who it suits
It suits teams that need a self-hosted schema registry and HTTP access to Kafka event production and consumption. It is also relevant to users working with Avro, JSON Schema or Protobuf schemas.
Plans and prices
Free and Open Source
Drop-in replacement · self-hosted or use with any managed provider
Read 30 Sep 2026 · karapace.io
On the record
- Authentication
- Schema Registry authentication supports HTTP basic authentication and OAuth2/OIDC bearer-token validation.karapace.io · read 30 Sep 2026
- High availability
- A leader/replica architecture provides high availability and load balancing across instances.karapace.io · read 30 Sep 2026
- Installation
- Karapace requires Python 3.12 or newer and can be installed from Docker images or source.karapace.io · read 30 Sep 2026
- Kafka compatibility
- Karapace implements the Confluent Schema Registry API and Confluent REST Proxy API v1 and v2, with v2 as the default.karapace.io · read 30 Sep 2026
- Maker relationship
- Aiven describes Karapace as an Aiven-built open-source Schema Registry and REST Proxy for Aiven for Apache Kafka.aiven.io · read 30 Sep 2026
- Monitoring integration
- Sentry error reporting can be enabled with the sentry configuration key or the SENTRY_DSN environment variable.karapace.io · read 30 Sep 2026
- Normalization limit
- Schema normalization is currently supported for Protobuf only, and Karapace does not implement every Confluent Schema Registry normalization feature.karapace.io · read 30 Sep 2026
- OAuth token handling
- The REST Proxy forwards OAuth2 tokens to Kafka and the Schema Registry instead of validating them itself.karapace.io · read 30 Sep 2026
- Observability
- Karapace exposes Prometheus-native metrics and integrates with OpenTelemetry for traces and metrics.karapace.io · read 30 Sep 2026
- Purpose
- Karapace is a free and open-source implementation of the Kafka Schema Registry and Kafka REST Proxy.karapace.io · read 30 Sep 2026
- REST proxy
- The REST Proxy provides HTTP APIs for producing and consuming Kafka events and performing administrative operations.aiven.io · read 30 Sep 2026
- Schema formats
- Karapace supports Avro, JSON Schema, and Protobuf schemas.karapace.io · read 30 Sep 2026
- Schema references
- Avro schema references are supported from Karapace version 6.1.0 onward, while JSON Schema does not support references in the documented table.aiven.io · read 30 Sep 2026
- Schema registry
- Its Schema Registry stores schemas centrally, maintains version histories, and checks compatibility between versions.karapace.io · read 30 Sep 2026
- Service endpoints
- The Docker setup exposes the Schema Registry on port 8081 and the REST Proxy on port 8082 by default.karapace.io · read 30 Sep 2026
