Compare OpenAPI specifications before you merge
A useful OpenAPI diff does more than list changed lines. It explains whether an endpoint, input, response or schema change can break an existing API consumer.
Compare behaviour, not formatting
Reordered YAML and rewritten descriptions should not fail a build. Contract Guard parses both specifications and compares the API operations and schemas they describe.
Identify consumer-breaking changes
Removed endpoints, removed success responses, new required parameters and narrower response schemas are reported as breaking changes with their exact contract location.
Start in the browser
Paste or upload two OpenAPI 3.x specifications into the free checker. Processing happens in the browser, so the files do not need to be sent to a server.
Move the rule into GitHub
Install the GitHub App to run the same compatibility check automatically when a pull request changes an OpenAPI JSON or YAML file.
Protect every pull request automatically
Install the GitHub App, choose a repository and get a clear pass or fail status whenever its OpenAPI contract changes.
Frequently asked questions
Can I compare YAML with JSON?
Yes. Both documents are parsed as OpenAPI structures, so the baseline and candidate can use different supported formats.
Does the free OpenAPI diff upload my files?
No. The public checker runs locally in the browser.
What is treated as a breaking API change?
Examples include removed operations or responses, newly required inputs, removed response properties and incompatible schema type changes.
Can the check block a pull request?
Yes. The GitHub App publishes a check run that can be made a required branch-protection status.