Free tool · runs in your browser
OpenAPI Diff Checker
Paste the old and new versions of an OpenAPI spec and compare them side by side — what was removed is highlighted in red, what is new in green. Then see which changes will break existing API clients, with a ready-to-run regression test for each.
Your specs never leave your computer. The comparison runs inside this browser tab; nothing is uploaded or stored.
| Old version | New version |
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Impact on API clients
Which of these changes break existing clients?
Every change rated breaking, warning or safe — with the regression test that would catch each break before it ships.
How it works
From a spec change to a safety net
See every line that changed
The two versions are lined up side by side. Removed lines are red, new lines are green, and the exact words that changed within a line are marked.
Understand the impact
Paths, parameters, request bodies, responses, enums and authentication are compared — with $ref and allOf resolved — and each change is rated for existing clients.
Catch it in CI
Generated tests encode what clients rely on today. Add them to your pipeline and an accidental break fails the build instead of a customer integration.
Want contract testing set up in your pipeline?
API test automation and CI quality gates are scoped pieces of work we deliver with a committed date. Tell us about your APIs and we will come back with a plan, a timeline and a fixed quote.