An API contract is not a public document
The specification of an internal API describes routes, fields and sometimes examples containing real data. It is a map of your system's attack surface. Pasting it into a hosted viewer means handing that map over; here the parsing happens in your tab and the contract never leaves your machine.
Works with OpenAPI 3.x and Swagger 2.0
It accepts both versions in either format, JSON or YAML. It resolves the schema and presents each operation with its parameters, request body and declared responses, without you having to spin up a Swagger UI instance.
What it is genuinely for, day to day
Reviewing a contract another team handed you before you start integrating, quickly finding which endpoint returns a particular field, or checking that a new version has not silently changed responses. With filtering by path, method or tag you reach the endpoint in seconds even when the contract holds hundreds.