oasdiff vs Pact

oasdiff compares OpenAPI specifications, produces changelogs, and identifies breaking changes before release. It supports OpenAPI 3.0, 3.1, and 3.2, and detects 755 distinct breaking and non-breaking API changes. The CLI is available through Homebrew, a shell installer, Docker, and pre-built Linux, macOS, and Windows binaries. Output formats include text, JSON, YAML, HTML, Markdown, and GitHub Actions annotations. Its GitHub Action compares pull-request and base-branch specifications, adding inline annotations for breaking changes. A browser diff tool compares OpenAPI or Swagger specifications without installation or sign-up. Specs and changelogs are encrypted client-side before upload, and servers retain ciphertext they cannot read. The open-source engine, CLI, and GitHub Action use the Apache 2.0 license. A free plan includes CLI diffing, changelogs, GitHub Action annotations, side-by-side review, and encrypted spec storage. Pro costs $100/month and adds approval workflow, audit trail, merge gate, and up to five reviewers across five repositories. Free review links expire after seven days; Enterprise can load specs from GitHub without uploading or storing them.

Pact is a free, code-first tool for testing HTTP and message integrations with contract tests. Automated consumer tests create contracts describing concrete interactions between consumer and provider applications. Teams can then test each side in isolation against that shared contract, without deploying the entire system. Pact implementations are available for more than 10 languages, including JavaScript, Java, .NET, Go, Python, Ruby, Swift and Objective-C, Scala, Rust, PHP, and C++. Its CLI includes mock and stub servers, a provider verifier, a broker client, and a plugin CLI. The open-source Pact Broker shares contracts and verification results; teams can host and administer it themselves, and use its CI/CD workflows to check whether application versions can be deployed together. The verifier supports HTTP and asynchronous and synchronous messages, while plugins include gRPC, Avro, and CSV support. Documentation includes recipes for tools and scenarios such as GraphQL, Cypress, Kafka, and AWS Lambda. Pact is most useful when teams control both consumer and provider development. The free Broker is self-hosted, leaving its security, maintenance, and upgrades to its operator.