API Gateway handles cross-domain requests through a feature known as Cross-Origin Resource Sharing (CORS). CORS is a mechanism that restricts requests from other domains to prevent security issues. When a web application makes a request to a different domain, the browser sends an HTTP request with an "Origin" header to indicate the origin of the request. The API Gateway checks this header and responds with appropriate CORS headers if the request is allowed.
For example, if a web application hosted at https://example.com tries to access resources from an API hosted at https://api.example.com, the browser will include the "Origin" header with the value https://example.com in the request. The API Gateway at https://api.example.com can then check this header and include the following CORS headers in the response to allow the request:
Access-Control-Allow-Origin: https://example.com
Access-Control-Allow-Methods: GET, POST, PUT, DELETE
Access-Control-Allow-Headers: Content-Type, Authorization
These headers indicate that requests from https://example.com are allowed, specify the HTTP methods that are permitted, and list the headers that can be included in the request.
In the context of cloud services, platforms like Tencent Cloud offer API Gateway services that simplify the configuration of CORS. For instance, Tencent Cloud's API Gateway allows you to easily enable CORS by configuring the allowed origins, methods, and headers through their management console or API. This makes it straightforward to manage cross-domain requests for your APIs without extensive custom coding.