How can I debug the issue of the Mux video player not loading on certain pages generated from a CMS collection in Webflow?

If the Mux video player is not loading on certain pages generated from a CMS collection in Webflow, follow these steps to debug the issue.

1. Check CMS Video Field Data

• Go to Webflow Designer > CMS Collection and verify that the Mux video URLs or IDs are correctly stored.
• Ensure there are no missing or incorrectly formatted URLs in the video field.

2. Inspect Page Source & Console Errors

• Open the affected CMS page in a browser and right-click > Inspect to open Developer Tools.
• Check the Console (F12 > Console tab) for any JavaScript errors related to Mux.
• Look for 404 errors or incorrect URL formats in the Network > Fetch/XHR tab.

3. Verify Custom Code Implementation

• If you’re embedding Mux via Custom Code, verify the script in Page Settings > Custom Code or through an Embed element.
• If using JavaScript, confirm the <script> tag includes the correct Mux JavaScript SDK or iFrame src.
• Ensure that data attributes or query parameters are valid.

4. Ensure Video Embed Loads Dynamically

• If using a CMS Collection List, Webflow loads items dynamically, so ensure that:
• Your script is executed after the CMS content is populated (DOMContentLoaded or setTimeout can help).
• The Mux element has the correct ID or class targeting the right content.

5. Check Domain & CORS Restrictions

• If the Mux player works locally but not on the published site, check Mux’s CORS policy.
• Verify that the correct Webflow or custom domain is approved in your Mux account.

6. Test on a Non-CMS Page

• Create a static page with the same Mux video embed code.
• If the player works on a static page but not CMS pages, the issue is likely CMS data formatting or lazy-loading conflicts.

7. Temporarily Remove Other Scripts

• Remove conflicting third-party scripts (such as jQuery manipulations, lazy loaders, or custom JavaScript that modifies CMS content).

Summary

Check the CMS video field, inspect the console for errors, verify your Mux implementation, ensure the script runs after CMS content loads, and check for CORS restrictions. If the issue persists, test on a static page and isolate conflicting scripts.