CORS: Understanding the 'Preflight' Request for Cross-Domain Requests
Cross-origin resource sharing (CORS) poses challenges when making HTTP requests across domains. To address these limitations, preflight requests have been introduced as a workaround.
Preflight Request Explained
Preflight requests are OPTIONS requests that precede actual requests (such as GET or POST) and serve to negotiate with the server regarding the request's permissions. These requests include two additional headers:
Configuring the Server Response
To handle preflight requests, the server must respond with the following headers:
Client-Side Preflight Implementation
For the preflight request to be successful, the client must include the following modifications:
Example:
Consider a preflight request for a POST request to fetch data from a remote URL.
Preflight Request:
Server Response (Assuming POST and X-Custom-Header are allowed):
Actual Request:
By following these steps, you can effectively preflight HTTP requests to overcome cross-domain limitations using CORS.
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