The Swagger UI demo is available at the following link.

Swagger UI
petstore.swagger.io

By appending ?url=(URL to a JSON or YAML file) to the above URL, you can specify the initial specification to display.

Here, we will use the following publicly available examples.

GitHub - OAI/OpenAPI-Specification: The OpenAPI Specification Repository
The OpenAPI Specification Repository. Contribute to OAI/OpenAPI-Specification development by creating an account on GitHub.
GitHub

For example, you can specify it as follows.

Swagger UI
petstore.swagger.io

I hope this serves as a useful reference when sharing specifications with others.