Free OpenAPI Diff Tool
Compare two OpenAPI specifications in JSON or YAML. The tool reports changes to the API structure instead of showing a line-by-line text diff, so formatting and key order do not bury the changes that matter.
How to Compare OpenAPI Specs
- Paste the original JSON or YAML specification into the Before field.
- Paste the updated specification into the After field.
- Review the detected semantic changes. Comparison starts automatically after both specifications are valid.
Your Specs Stay in the Browser
The current tool parses and compares pasted specifications in a browser worker using WebAssembly. Your OpenAPI content is not sent to a comparison API or stored by the tool.
No account is required. Avoid pasting secrets into any API specification; credentials do not belong in an OpenAPI file.
Semantic Diff, Not Breaking-Change Classification
A text diff treats whitespace, reordering, and formatting as changes. Restly compares the parsed API descriptions and surfaces structural changes such as updated operations, responses, parameters, and schemas. The tool does not currently assign a breaking/non-breaking label or recommend a semantic-version bump; review each reported contract change in the context of your API.
For the design decisions around evolving a contract, read our REST API versioning guide. To catch consistency problems before comparing versions, see the OpenAPI linting guide.
When an OpenAPI Diff Is Useful
- Review an API contract before a release or client migration.
- Verify that importing and exporting a specification did not alter its structure.
- Inspect changes between a production contract and a draft branch.
- Separate meaningful API changes from YAML formatting noise in a code review.
Restly also runs this semantic comparison inside its visual OpenAPI editor before a branch is saved. See how that workflow compares on the Stoplight alternative page.