No. 12 of 22 ·Contract Testing Tools

Karapace

Self-hosted · API

Freedom report

Two barsScore 6.3

Free tierA free tier is on its own pricing page
Open codeNo open-source code on record
Runs widely0 of 6 device platforms
DocumentedPlans, terms and facts published

Karapace is ranked #12 of 22 in contract testing tools on Freedom251. It runs on API, Self-hosted. There is a free plan.

Karapace plans and pricing

All plans

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

Compared on contract testing tools

Free plan: Yes
Contract formats: Avro, JSON Schema, Protobuf
Consumer verification: No
Provider verification: No
Contract registry: Yes
AsyncAPI support: No
GraphQL support: No
Self-hosted deployment: Yes

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The record

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

Where it ranks on Freedom251

Best Contract Testing Tools in 2026#12 of 22

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Sources

karapace.io· checked 30 Sept 2026
karapace.io/docs/· checked 30 Sept 2026
karapace.io/docs/compatibility/· checked 30 Sept 2026
aiven.io/docs/products/kafka/karapace· checked 30 Sept 2026
karapace.io/docs/deployment/· checked 30 Sept 2026
karapace.io/docs/observability/· checked 30 Sept 2026
karapace.io/docs/authentication/· checked 30 Sept 2026
karapace.io/docs/install/· checked 30 Sept 2026