Connected App is required to connect Salesforce GraphQL API from Postman client.

1. Create a Connected App in Salesforce.

Callback URL should be https://{Your Domain}.my.salesforce.com/services/oauth2/callback

Example:

https://test-ec-dev-ed.develop.my.salesforce.com/services/oauth2/callback

2. Get the Access token.

Endpoint URL:

https://test-ec-dev-ed.develop.my.salesforce.com/services/oauth2/token

3. Use the Access Token from Step 2 in the Header and make a POST Request to the GraphQL API endpoint.

Endpoint:

https://test-ec-dev-ed.develop.my.salesforce.com/services/data/v59.0/graphql