How to resolve CORS errors in Magento 1 or 2 multi-stores using a CDN

Cross-origin request blocked (CORS) errors have many possible causes. This article applies to the “Cross-Origin Request Blocked error” that is sometimes the result of a Magento multi-store making use of a CDN.

Many businesspeople wonder How Does a CDN Work to Speed Up Your Ecommerce Site? but they will discover that the reasons are remarkably straightforward. Review the content, resources, and links in this article to learn more about those reasons in full detail.  

Problem

I have set up my Magento (1 or 2) multi-store to pull static assets from my Nexcess CDN, but browsers attempting to visit my store present a “Cross-Origin Request Blocked” error in the developer console:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at <your_website>

Cause

When functioning correctly, cross-origin resource sharing (CORS) allows one site access to another site’s resources despite having different domain names.

When using different hosts (such as a CDN host) to serve portions of your site, you must inform the browser that the third party host is safe to use. Otherwise, the browser assumes the third party host is malicious and blocks it.

 Read Magento 1 vs Magento 2: Should You Stay or Should You Go?

Solution

ATTENTION: This solution requires editing your .htaccess file. If you are unfamiliar with .htaccess and are a Nexcess client, please contact our support team from your Client Portal or by email.

To resolve this issue, access your server using SSH and edit the .htaccess file in your website’s root directory as shown below. If you are a Nexcess Classic (non-Cloud) client, you must first enable SSH access. Nexcess Cloud clients have SSH access by default.

In your .htaccess file, insert the line shown below, but replace the angled brackets (<>) and everything between them with the indicated information. If necessary, identify the customer origin URL by accessing the CDN Control Panel as shown in How to configure a CDN customer origin server, but do not use the entire URL; use only the domain name as shown in the example below:

<IfModule mod_headers.c>
   <FilesMatch "\.(ttf|ttc|otf|eot|woff|woff2|font.css|css|ico|js|json|html)$">
     Header set Access-Control-Allow-Origin "<customer_origin_domain>"
     Header set Access-Control-Allow-Headers "X-Requested-With"
   </FilesMatch>
</IfModule>

For 24-hour assistance any day of the year, contact our support team by email or through your Client Portal.