When using Azure Translator REST API, required headers are: Ocp-Apim-Subscription-Key # subscription key Ocp-Apim-Subscription-Region # resource region (if using a multi-service Cognitive Services resource) Content-Type # typically application/json or application/xml Other options: Client trace ID is optional for debugging. Resource ID, access control request, content language, content length are not required headers. Reference: Azure Translator API reference