To run your GraphQL operations simply choose the operation you want to run and click the Play button to execute.
To change URL and/or headers use the dropdown submenu at the top and add a new endpoint.
If you just want to test your API with GraphQL Editor you don't have to worry about CORS. Every request to your GraphQL API is proxied via our service to ensure no CORS issues.
You can connect to the API you are serving locally. Just type the localhost URL and it should work with your local backend.