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Keep old and new in the right order
Risk is judged for consumers of the older contract. Swap reverses that direction, so it opens a preview and the previous inputs and result can be restored once.
API contract tools
OpenAPI diffReview changes before release
Paste an older and a newer specification; compare only when you are ready.
OpenAPI diff
Older specification
Newer specification
Change report
Both specifications are processed in this browser; no API request is sent.
Comparison options
Scope: tracked request endpoints, parameters, request bodies and responses. A static report cannot prove runtime compatibility.
Paste both specifications to compare.
An OpenAPI diff is useful when a release changes a contract that existing clients already use. A text diff can hide whether a deleted route or a new required parameter changes valid calls.
Use this page to compare OpenAPI specs side by side, including Swagger 2.0 documents. The report keeps uncertain API contract changes in a review category instead of calling them safe.
Why use this OpenAPI diff
See the direction of risk
The OpenAPI diff reads the older contract against the newer one. Removing a response field is flagged differently from adding a route, so an upgrade review starts with the calls that may stop working.
Keep exclusions visible
An exact path exclusion removes that route from both sides and lists it in the report. Reviewers can tell which endpoints were intentionally left out, without guessing how a wildcard matched.
Three decisions that make the comparison useful
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Exclude only an exact path
Enter one OpenAPI path key per line, such as /internal/health. This is not a regular expression or JSON Pointer; changing it makes the existing report stale.
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Read the category before exporting
Breaking findings are potential client failures. Review findings need human context. The filter changes only the visible list; JSON and Markdown exports contain the complete fresh report.
Contract changes this comparison tracks
Routes and methods
A deleted method or path is flagged as potentially breaking; a newly declared endpoint is listed separately. This makes OpenAPI breaking changes easier to audit than a line diff.
Inputs and responses
Required parameters, required request fields, removed responses and removed response properties are checked. Simple type and enum changes are reported where the local schema can be resolved.
Evidence you can hand off
Each finding carries a method, path, rule and before/after values. Export a complete JSON or Markdown report after comparing; the visible category filter never deletes evidence.
What the static contract review can and cannot claim
- No remote fetch
- Paste JSON or YAML locally. This Swagger diff does not fetch a URL, call your API or upload either specification.
- Exact exclusions only
- Ignored paths must match a complete OpenAPI path key. Wildcards, regex and callback routes are outside this first comparison.
- Incomplete references stop the report
- External $ref, unsupported dialects, callbacks and webhooks block a fresh risk report. Missing or invalid local references also fail validation.
- No runtime proof
- A static contract report cannot prove how a live server or every SDK behaves. Test affected consumers before treating a release as compatible.
OpenAPI diff questions
What is an OpenAPI diff?
An OpenAPI diff compares the older and newer API descriptions by operation and supported schema rules. This page separates potential breakage, uncertain changes and compatible additions; it does not certify a deployment.
Does this work with Swagger files?
Yes. Swagger 2.0 as well as OpenAPI 3.0 and 3.1 JSON or YAML are parsed. Comparing across versions may still require manual review of changed request and response semantics.
How do I find breaking changes between two API specs?
Paste both versions and run the comparison. Removed routes, newly required inputs and removed response fields appear in the breaking category; inspect the rule and before/after evidence for each finding.
Is it free, and do I need to install anything?
The OpenAPI diff runs in your browser and requires no installation or account. It does not send either pasted specification to an API endpoint.
What output formats are supported?
Copy or download the full structured JSON report, or download Markdown for a review. There is no HTML, CI gate or share link.
Was this comparison useful?
Run an OpenAPI diff before the next release
An OpenAPI diff gives reviewers a specific list of contract changes and explicit limits. Pair it with consumer tests before shipping.