Put two versions side by side.
Paste or open local JSON files. Your contracts stay in this browser tab; declared API endpoints are never called.
Contract review, before release
Small changes.
Long shadows.
A field of new requirements. A response that quietly disappears. Find the contract changes your next release needs to account for.
OpenAPI 3.x JSON · Runs in your browser · No sign-up
THE REVIEW DESK01 / CONTRACTS
BEFOREv1.0
GET /parcels/{id}
"properties": {"trackingUrl": {"type": "string"}}
AFTERv1.1
GET /parcels/{id}
"properties": {− "trackingUrl"}
BreakingRESPONSE
A field went missing.
Check clients that read trackingUrl.
#/components/schemas/Parcel
Illustrative example · not an analysis resultINPUT → EVIDENCE → ACTION
A different starting point
Don't send a request.
Read what changed first.
Inspectable evidence.
A checklist you can take with you.
From contract to confidence
Less guesswork.
A clearer review.
Not another API client. A focused desk for comparing the promise your API makes.
Trace each change to its source.
Review breaking, additive and uncertain changes with JSON Pointer evidence. Inspect the before and after, not just a label.
Leave with a release checklist.
Get suggested tests and migration actions. Download the full review as Markdown or JSON, ready for your own review process.
Useful by design. Limited by design.
A reviewer,
not a guarantee.
DiffHaven checks a targeted set of structural changes in OpenAPI 3.0 and 3.1 JSON. It is not a complete validator, live API test runner, or proof of compatibility.
Composition, advanced schema constraints and other unsupported areas are disclosed in review warnings. Findings, explanations and test suggestions come from deterministic browser-side rules, not AI.
Read the coverage notesMake room for a careful release
Your next API change
deserves a second look.
Open the review desk Start with the fictional parcel API sample. No files needed.