When Axios returns an error 503 (Service Unavailable) while Postman returns the correct result, it indicates that the server is reachable, but it is temporarily unable to handle the request. The 503 error status code is typically used by servers when they are overloaded, undergoing maintenance, or facing some temporary issue that prevents them from handling incoming requests.

Here are some possible reasons for this discrepancy and steps to troubleshoot the issue:

  1. Rate Limiting or Overload:

    • The server might be experiencing high traffic or rate limiting requests. Postman might not be affected because it sends fewer requests compared to your application.
    • Check if the server has any rate-limiting policies in place, and ensure that your application is not sending an excessive number of requests.
  2. CORS Issue:

    • If your application is running in a different domain, there might be a Cross-Origin Resource Sharing (CORS) issue. Postman, being a standalone application, doesn't have the same restrictions as a web application.
    • Make sure the server is properly configured to handle CORS requests, and your application's requests are not being blocked.
  3. Headers and Payload Differences:

    • Check the headers and payload being sent by both Axios and Postman. Ensure they are identical, as some servers might behave differently based on specific request headers.
    • Compare the exact request being sent by Axios and Postman, including headers, query parameters, and request body.
  4. Cookies or Authentication:

    • If the server relies on cookies or authentication, ensure that Axios is handling cookies correctly, and authentication tokens (if any) are included in the request headers.
    • Postman might handle cookies and authentication automatically, but Axios might need explicit handling.
  5. TLS/SSL Certificate Issue:

    • Some servers might have strict security settings, and Axios could be more sensitive to SSL certificate issues compared to Postman.
    • Ensure that your server's SSL certificate is valid and correctly configured.
  6. Proxy Settings:

    • Check if your application or system has any proxy settings that might be interfering with Axios requests.
    • Postman might have separate proxy configurations, leading to different behavior.
  7. Server-Side Issue:

    • There might be a server-side misconfiguration or issue that is causing the 503 error for specific requests from your application.
    • Review server logs or contact the server administrator for more information.

To troubleshoot the issue further, you can use the browser's developer tools to inspect the network requests made by your application using Axios. Look for any error messages, response headers, or differences compared to Postman's requests. Additionally, consult the server's documentation or contact the server administrators to understand potential issues from their end.

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