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 a CORS (Cross-Origin Resource Sharing) issue when trying to access the Webflow API from a browser. The API blocks frontend requests from different origins for security reasons.

1. Understand Webflow API Access Limitations

• The Webflow API is designed to be used server-side, not in the browser.
• If you call the API client-side (e.g., from JavaScript in a Webflow project), the request is blocked due to CORS policy.
• Webflow's API does not include CORS headers like Access-Control-Allow-Origin, so browsers will deny access.

2. Use a Server-Side Proxy

• Set up a backend proxy (e.g., Node.js with Express, or even use tools like Vercel Serverless Functions or Cloudflare Workers).
• Make your frontend send the request to your backend; your backend then calls the Webflow API.
• This avoids CORS because the actual API request is made server-to-server — not in the browser.

3. Do Not Embed API Calls in Webflow's Frontend JS

• Avoid using fetch() or XMLHttpRequest directly to https://api.webflow.com from your site's JavaScript.
• Doing so will always result in a CORS error and block the request.

4. Required Headers for Webflow API (from Server)

• When making requests to the Webflow API from your backend, include:
• Authorization: Bearer YOUR_SITE_API_TOKEN
• Content-Type: application/json
• accept-version: e.g., 1.0.0 (based on the API version you're using)

5. Use Environment Variables to Secure Your API Key

• Never expose your Webflow API token in client-side code.
• Use environment variables on your backend to keep credentials safe.

Summary

Webflow blocks client-side API calls due to CORS restrictions. Use a server-side proxy to call the API securely and avoid browser-based CORS errors. Always keep your API key server-side to prevent misuse.