OpenAPI & GraphQL tools
API contract work involves more than writing YAML: reviewing whether a schema change breaks existing clients, turning a Postman collection a colleague shared into a spec you can version, or generating realistic fixtures before a backend endpoint even exists. These tools cover OpenAPI and GraphQL editing, diffing and mocking, plus a Postman-to-OpenAPI converter and a curl command generator for testing individual requests.
Use the OpenAPI diff or GraphQL schema diff specifically to catch breaking changes — removed fields, changed types, tightened arguments — between two versions before a release. The OpenAPI mock generator produces request and response JSON straight from your operations, so a frontend can start against realistic data before the real API ships. All of it runs in the browser on the spec you paste in.
7 tools
All OpenAPI / GraphQL / Postman tools
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Postman to OpenAPI
Convert Postman collections to OpenAPI with request inspection
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OpenAPI editor
Edit Swagger 2.0 and OpenAPI 3.x specifications with validation
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OpenAPI diff
Compare two API specifications to review changes and breaking risks
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OpenAPI mock generator
Generate request and response JSON fixtures from API operations
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GraphQL workbench
Format GraphQL queries, SDL and variables with optional schema validation
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GraphQL schema diff
Compare GraphQL schemas to identify type, field and argument changes
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cURL converter
Generate Fetch, Axios and Python from curl commands or JavaScript
OpenAPI / GraphQL / Postman tools FAQ
Run both spec versions through the OpenAPI diff to see added, removed and changed paths, parameters and schemas side by side. Removed fields, newly required parameters and narrowed types are the changes most likely to break a client already working against the old spec.
Yes — the Postman to OpenAPI converter reads a Postman collection export and rebuilds it as an OpenAPI document, including the requests it can inspect. It's a starting point for a spec you can then refine in the OpenAPI editor rather than a fully automatic, lossless conversion.
A REST diff compares paths, methods, parameters and JSON schemas across an OpenAPI document. A GraphQL schema is a single typed graph, so the GraphQL schema diff instead compares types, fields and arguments directly, which is what actually determines whether an existing query still resolves.