How can I get Webflow to allow access to the API and stop blocking the cross-origin response with MIME type application/json?

You're encountering an issue where Webflow is blocking a cross-origin API request because of CORS (Cross-Origin Resource Sharing) or incompatible MIME type settings. Here's how to address it:

1. Understand Why It's Blocked

• Webflow’s Hosting is secure and will not automatically allow external API responses inside client-side scripts if CORS headers aren’t correctly set.
• Most common cause: The API server must return Access-Control-Allow-Origin: * (or a specific origin) in its response headers.

2. Fix or Bypass CORS on Your API

• If you control the API server: Add the header Access-Control-Allow-Origin: * for all responses, especially those serving application/json.
• If you don’t control the server: Use a CORS proxy temporarily like cors-anywhere or services like https://api.allorigins.win.
• Example: Instead of fetching directly from https://api.example.com/data, fetch https://api.allorigins.win/raw?url=https://api.example.com/data.

3. Use Webflow’s Native Tools Wisely

• No server-side handling: Remember, Webflow hosting is static. You can't manage server headers directly from Webflow unless using an external service like AWS Lambda, Netlify Functions, or Make (formerly Integromat).
• Use custom code embeds when calling APIs, but you're still limited by browser-side CORS rules.

4. Confirm Correct MIME Type

• The API should return Content-Type: application/json for JSON responses.
• Webflow does not alter MIME types. If the server sends the wrong MIME type (like text/html), browsers will block it under CORS rules regardless.

5. If Needed, Use a Backend Proxy

• Backend proxy rule: Create a small server (like on Heroku, Vercel, or Netlify) that fetches the API server-side and returns it to your Webflow site with proper CORS headers.
• Benefit: Your Webflow site will talk only to your proxy, avoiding CORS entirely.

Summary

You must make sure that the external API’s server sends Access-Control-Allow-Origin headers and correctly sets the Content-Type to application/json. If you can't control the server, use a CORS proxy or create a backend proxy to handle the API requests safely for your Webflow project.