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CORS Issue Persisting on Frontend Web App Despite Configuration

Devanshu Soni 0 Reputation points
2025-07-29T12:08:46.7366667+00:00

We are facing a recurring CORS (Cross-Origin Resource Sharing) issue on our frontend web application, even though the necessary CORS policies have already been configured and allowed on the backend/API side.

Despite allowing the required origins in our CORS settings, the frontend continues to encounter CORS-related errors. We've verified that:

The allowed origin is correctly specified in the backend/API configuration.

The frontend request is using the correct method and headers.

No browser or caching issues are interfering.

Could you please help us identify what might be causing this issue to persist or if there's anything we might be missing in our Azure/App Service or API Management configuration?

Environment Details:

Frontend: NextJS

Backend: Node.js

Hosted on: Azure App Services

Azure App Service
Azure App Service
Azure App Service is a service used to create and deploy scalable, mission-critical web apps.
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  1. Vishvani Jilukara 5 Reputation points Microsoft External Staff Moderator
    2025-08-11T13:30:50.6166667+00:00

    Hi Devanshu Soni,
    Given your environment (Next.js frontend, Node.js backend, hosted on Azure App Services), and the fact that you've already configured CORS on the backend, here are a few areas worth double-checking, especially when using Azure App Services and possibly Azure API Management (APIM):

    1. If Using Azure API Management (APIM):

    CORS policies must be explicitly configured in APIM, as OPTIONS (preflight) requests often don’t reach the backend.

    Please check your inbound policy in the APIM API definition and ensure it includes a <cors> block. lf CORS is only configured at the backend and not in APIM, the browser will block the response due to missing CORS headers on the preflight.

    2.Azure App Service Specifics:

    If you're directly calling the backend via App Service (and not via APIM), ensure:

    • HTTPS is enforced on both frontend and backend (HTTPS Only enabled under TLS/SSL settings in App Service).
    • No redirection occurs that may strip CORS headers.

    You're calling the backend using the correct domain (e.g., https://your-api.azurewebsites.net or custom domain).

    1. Backend Node.js (Express) CORS Setup:

    Ensure the CORS middleware is correctly set up and registered before your route handlers

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