Karapace vs Specmatic

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.

Specmatic turns API specifications into executable contracts for designing, building, and governing APIs. Its suite includes Genie, which generates API specifications from plain English; Studio for visual API workflows and contract testing; and Insights for API governance and analytics. Listed formats include OpenAPI, AsyncAPI, Avro, GraphQL SDL, Protobuf, WSDL, and Arazzo. Protocols include HTTP/REST, Kafka, gRPC, GraphQL, Google Pub/Sub, JMS, MQTT, RabbitMQ, SOAP, WebSocket, and MCP. The free Open Source plan includes contract and API resilience testing, service virtualization, backward compatibility testing, a proxy server, and a specification coverage report. Enterprise adds Studio and Insights, available as SaaS or on-premise, alongside additional protocol and workflow capabilities. The software supports Linux, macOS, Windows, and self-hosted environments, with installation options including shell and PowerShell scripts, npm, and pip. A free plan is available; the pricing note lists paid access from $10/user/mo (annual).