Why does hosting external resources on a subdomain not resolve the "Access-Control-Allow-Origin missing" error in Webflow? Is it because the Webflow site is not hosted on the same server as the subdomain and is only pointed to with an A record? Is there another solution or a way to set header policies in Webflow to address this issue?
TL;DR
- CORS errors occur when external resources lack the appropriate
Access-Control-Allow-Originheaders, even if served from a subdomain. - To fix this, host resources on a server or service that lets you set CORS headers, since Webflow doesn’t support header configuration.
- Alternatively, avoid CORS by uploading assets directly to Webflow or using trusted third-party embeds.
The "Access-Control-Allow-Origin missing" error occurs when assets loaded from a different origin (like a subdomain) aren't served with the appropriate CORS headers. This is not resolved simply by pointing a subdomain at a server using an A record if the server doesn't send the correct CORS headers.
1. CORS Enforcement in Browsers
- Browsers enforce Cross-Origin Resource Sharing (CORS) to prevent unauthorized requests across different origins.
- Even if your external resource is hosted on a subdomain (e.g.,
assets.yoursite.com), it’s still considered a different origin fromwww.yoursite.comdue to the hostname difference.
2. Why a Subdomain Alone Doesn’t Solve It
- A records only point the DNS of a subdomain to an IP address; they have no effect on how the server at that address handles HTTP headers.
- Your subdomain needs to be backed by a server (like Amazon S3, Cloudflare R2, or similar) that explicitly adds the
Access-Control-Allow-Originheader to allow cross-origin access.
3. Webflow Hosting Limitations
- Webflow does not give you access to response headers like
Access-Control-Allow-Origin. - You cannot set CORS policies or custom headers directly from your Webflow site’s settings.
4. Proper Solution Using External Hosting
- Host your external resources (fonts, media, JS files, etc.) on a server or service that you control or configure.
- Set the server or CDN to return these headers, e.g.:
Access-Control-Allow-Origin: *(for public assets)- Or
Access-Control-Allow-Origin: https://www.yoursite.com(for restricted access) - Common platforms where you can configure these headers:
- Amazon S3/CloudFront (via CORS config)
- Cloudflare R2 Workers (via custom headers)
- Netlify, Vercel, Firebase (using headers configuration)
5. Alternatives Within Webflow’s Limits
- Avoid external hosting and upload assets directly to Webflow’s CMS or assets panel. These are served from the same origin and therefore don't trigger CORS errors.
- Use only embedded third-party services (like YouTube, Vimeo) that handle CORS headers for you when embedded via iframe.
Summary
Simply using an A record to point a subdomain to a server doesn't resolve CORS errors unless that server is properly configured to send Access-Control-Allow-Origin headers. Webflow doesn’t allow editing response headers, so you must host these external assets elsewhere and ensure that destination sends proper CORS headers.