# API Breaking Changes Detector & Migration Planner Compare two OpenAPI 3.x schemas, identify breaking changes, grade client impact, and suggest migration or compatibility strategies > Canonical page: https://elysiatools.com/en/tools/api-breaking-changes-detector-migration-planner - **Category:** Development - **Keywords:** openapi, api diff, breaking change, migration, schema, contract testing, swagger ## Overview Paste old and new OpenAPI schemas in JSON or YAML to detect removed endpoints, request contract tightening, response field removals, and other changes likely to break generated SDKs or downstream clients. ## Inputs - **Old OpenAPI Schema** (textarea): openapi: 3.0.3 paths: /users: ... - **New OpenAPI Schema** (textarea): openapi: 3.0.3 paths: /users: ... ## When to use - Before releasing a new API version to ensure downstream clients and generated SDKs will not break. - When reviewing pull requests that modify OpenAPI specifications to catch unintended contract tightening. - During API migration planning to document required client-side updates and communicate them to consumers. ## How it works - Paste your original OpenAPI 3.x schema (JSON or YAML) into the Old OpenAPI Schema field. - Paste the updated specification into the New OpenAPI Schema field. - The tool parses both schemas to perform a deep structural diff, specifically looking for removed fields, new required parameters, and type changes. - Review the generated HTML report to see a graded list of breaking changes and recommended migration paths. ## Use cases - Preventing SDK generation failures by catching removed response properties before merging API updates. - Auditing third-party API updates to understand how a vendor's new version will impact your integration. - Generating changelogs and migration guides for developer portals when releasing a major API version. ## Frequently asked questions ### What formats are supported for the schemas? The tool accepts OpenAPI 3.x specifications in both JSON and YAML formats. ### What qualifies as a breaking change? Breaking changes include removing endpoints, deleting response fields, changing data types, or adding new required request parameters. ### Does this tool validate my OpenAPI syntax? While it parses the structure to compare them, it is designed for diffing and detecting contract changes rather than strict linting or syntax validation. ### Can it detect non-breaking changes? The primary focus is on identifying breaking changes that impact client compatibility, such as contract tightening or field removals. ### Is my API schema data stored on your servers? 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