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Karapace

karapace.io

Free plan APISelf-hosted
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Spec score 7.9 #12 of 22 in Contract Testing Tools

What it is

Karapace is a free, open-source implementation of the Kafka Schema Registry and Kafka REST Proxy. Its registry stores Avro, JSON Schema, and Protobuf schemas, keeps version histories, and checks compatibility between versions. The REST Proxy exposes HTTP APIs for producing and consuming Kafka events and handling administrative operations. 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 provides high availability and load balancing. Monitoring includes Prometheus-native metrics and OpenTelemetry traces and metrics, with optional Sentry reporting. Schema Registry authentication supports HTTP basic authentication and OAuth2/OIDC bearer-token validation; the REST Proxy forwards OAuth2 tokens instead of validating them. Karapace is self-hosted, requires Python 3.12 or newer, and installs from Docker images or source. Default Docker ports are 8081 for the Schema Registry and 8082 for the REST Proxy. It is offered at free.

Spec sheet

Purpose
Karapace is a free and open-source implementation of the Kafka Schema Registry and Kafka REST Proxy.Read 30 Sep 2026 · karapace.io
Headquarters
Helsinki, FinlandRead 28 Sep 2026 · karapace.io
Founded
2020Read 28 Sep 2026 · karapace.io
Authentication
Schema Registry authentication supports HTTP basic authentication and OAuth2/OIDC bearer-token validation.Read 30 Sep 2026 · karapace.io
High availability
A leader/replica architecture provides high availability and load balancing across instances.Read 30 Sep 2026 · karapace.io
Installation
Karapace requires Python 3.12 or newer and can be installed from Docker images or source.Read 30 Sep 2026 · karapace.io
Kafka compatibility
Karapace implements the Confluent Schema Registry API and Confluent REST Proxy API v1 and v2, with v2 as the default.Read 30 Sep 2026 · karapace.io
Maker relationship
Aiven describes Karapace as an Aiven-built open-source Schema Registry and REST Proxy for Aiven for Apache Kafka.Read 30 Sep 2026 · aiven.io
Monitoring integration
Sentry error reporting can be enabled with the sentry configuration key or the SENTRY_DSN environment variable.Read 30 Sep 2026 · karapace.io
Normalization limit
Schema normalization is currently supported for Protobuf only, and Karapace does not implement every Confluent Schema Registry normalization feature.Read 30 Sep 2026 · karapace.io
OAuth token handling
The REST Proxy forwards OAuth2 tokens to Kafka and the Schema Registry instead of validating them itself.Read 30 Sep 2026 · karapace.io
Observability
Karapace exposes Prometheus-native metrics and integrates with OpenTelemetry for traces and metrics.Read 30 Sep 2026 · karapace.io
REST proxy
The REST Proxy provides HTTP APIs for producing and consuming Kafka events and performing administrative operations.Read 30 Sep 2026 · aiven.io
Schema formats
Karapace supports Avro, JSON Schema, and Protobuf schemas.Read 30 Sep 2026 · karapace.io
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.Read 30 Sep 2026 · aiven.io
Schema registry
Its Schema Registry stores schemas centrally, maintains version histories, and checks compatibility between versions.Read 30 Sep 2026 · karapace.io
Service endpoints
The Docker setup exposes the Schema Registry on port 8081 and the REST Proxy on port 8082 by default.Read 30 Sep 2026 · karapace.io

Plans and prices

Free and Open Source Free Drop-in replacement · self-hosted or use with any managed provider Read 30 Sep 2026 · karapace.io

Every Karapace plan and price →

Strong points and limits

Strong points

  • Supports Avro, JSON Schema, and Protobuf
  • Confluent API compatibility
  • High availability and load balancing
  • Prometheus and OpenTelemetry integration
  • Free and open source

Limits

  • Self-hosted deployment required
  • Requires Python 3.12 or newer
  • JSON Schema references are unsupported
  • Normalization is limited to Protobuf

Who it suits

It suits teams running Kafka that need a self-hosted schema registry and REST interface compatible with Confluent APIs. Operators should be comfortable with Python 3.12 or newer and Docker or source installation.

Verdict

Karapace provides registry and REST capabilities for Kafka deployments without a license charge. Its self-hosted setup and documented schema limitations are important for architecture and compatibility planning.

Where Specifiction places it

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Pact From $115.42/mo · Free plan 8.7 Visit