OpenAPI Diff Checker

A breaking change is anything that requires existing clients to update their code. Examples include: removing an endpoint, changing an HTTP method, removing a required request field, adding a new required field, changing a field's type, or changing a status code. Non-breaking changes include: adding optional fields, adding new endpoints, or loosening validation constraints.

This tool supports OpenAPI 3.x and Swagger 2.x specifications in JSON or YAML format. Paste the full spec text including the openapi/swagger version field. The parser handles both formats automatically.

API consumers (mobile apps, third-party integrations, internal services) depend on your API contract. Breaking changes silently break their code. Detecting them before releasing a new version lets you communicate changes, version your API, or provide migration guides.

This tool performs structural diff analysis on paths, methods, parameters, and response codes. It does not execute the APIs, check authentication behavior, or detect semantic changes in business logic. Use contract testing frameworks like Pact for full consumer-driven contract testing.

Common strategies: bump the major version (v1 → v2) and run both versions in parallel, use deprecation headers to notify clients, provide a migration guide, or use API gateways to transform old requests to new formats.