Compare two OpenAPI specifications

Compare two OpenAPI contracts and flag client-visible changes.

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Input
Output
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How it works

Documents are normalized by paths, operations, parameters, bodies, responses, schemas, and security; differences are classified as additions, removals, or behavior changes. Severity reflects whether a client contract narrowed or widened.

  • Removed operations and required inputs are breaking changes.
  • Widening a response is usually safer than narrowing it.

Worked example

Compare API Versions
Detect differences between two versions of an OpenAPI spec
Input
											Input1: {"openapi":"3.0.3","info":{"title":"API","version":"1.0.0"},"paths":{"/users":{"get":{"summary":"List users"}}}}
Input2: {"openapi":"3.0.3","info":{"title":"API","version":"2.0.0"},"paths":{"/users":{"get":{"summary":"List all users"}},"/posts":{"get":{"summary":"List posts"}}}}
Output
												Path                        Type     Details
--------------------------  -------  ---------------------------------------------------
$.info.version              changed  Value changed from "1.0.0" to "2.0.0"
$.paths./users.get.summary  changed  Value changed from "List users" to "List all users"
$.paths./posts              added    New property added

When to use this

Release CI, gateway migrations, and API version reviews compare OpenAPI.

Edge cases

  • Adding a required request field breaks existing clients.
  • Removing an enum value can break clients.
  • Changing nullable response fields affects generated types.

References