OpenAPI Specification Diff Checker

Compare two OpenAPI specs and list added, removed and changed endpoints.

Runs in your browser. Nothing is uploaded — your input is processed on this device and discarded when you close the tab.

OpenAPI Specification Diff Checker

How to use this tool

  1. Paste the old spec in the first box and the new spec in the second.
  2. Click Run to see added endpoints, removed endpoints and operations whose parameters or responses changed.
  3. Load the sample for a before/after pair where one endpoint is added and one response changes.

Worked example

The sample old spec has GET /users only; the new spec adds POST /users and changes GET /users to return an extra field. The diff reports one added endpoint (POST /users), no removals, and one changed operation (GET /users, response schema changed).

What this tool does not do / Limits

Specs may be JSON, or YAML limited to indentation-based maps and lists with scalar values (the subset most hand-written OpenAPI files use). Full YAML features — anchors, multi-line blocks, complex keys — are not parsed and will report a parse error rather than a partial diff. Comparison covers paths, operations, operation parameters and response status codes plus response schema shape; it does not deep-compare every schema keyword.

Frequently asked questions

Why did my YAML fail to parse?

This tool's YAML reader handles plain maps, lists and scalars only. Anchors (&x / *x), block scalars (| and >) and quoted multi-line strings fall outside that subset — convert the file to JSON for a full diff.

Does it detect breaking changes?

It lists what changed; whether a change breaks clients is a judgement call. Removed endpoints and removed response fields are the usual breaking signals, and both appear in the diff.

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