What is API contract testing?

API contract testing checks that a provider and consumer agree on request and response shapes, required fields, types, and compatibility across versions.

What is a breaking API change?

Removing a field, changing a field type, adding a new required field, or changing a response shape can break an existing API consumer.

Does this checker upload schemas?

No. The comparison runs in the browser. Do not paste confidential schemas if your organization does not allow them in browser tools.

OpenAPI Contract Testing

API Contract Testing

Compare two JSON or OpenAPI schema versions and find likely breaking changes before a provider release reaches its consumers. The check runs locally in your browser.

Compare contracts API integration testing API testing tools

OPENAPISCHEMADIFFBREAKING

DIFF

Compatibility check

Catch risky schema changes early.

Schema comparison

Compare old and new API contracts.

Paste JSON objects containing a properties object, or a full OpenAPI document with component schemas.

Contract reportREADY

API contract testing checklist

Compare request fields, response fields, data types, enums, required properties, status codes, error shapes, authentication requirements, pagination, and versioning rules. A compatible change usually adds optional behavior; a breaking change removes or restricts behavior that an existing consumer relies on.

OpenAPI contract testing

For an OpenAPI document, focus on the paths and schemas that changed between versions. Run the comparison during pull requests, then use the API integration testing tool to exercise important examples against a deployed environment.

Release workflow

Keep fictional fixtures in the test data generator, document risk and entry/exit criteria in the test plan template, and turn a failed compatibility check into a Jira test case.

API contract testing FAQ

What changes are usually breaking?

Removed properties, changed types, newly required properties, narrowed enums, incompatible status codes, and altered error or authentication contracts are common breaking changes.

Is this a full OpenAPI validator?

No. This focused checker covers common properties, required fields, types, enums, and OpenAPI component schema changes. Use a full schema validator and CI contract suite for release gates.

Are schemas sent to a server?

No. Comparison runs in the current browser tab. Avoid pasting confidential or proprietary schemas where policy does not allow it.