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Minimal CSP addition

CSP is the #1 cause of “Builder won’t open.” If your site has a strict CSP and you haven’t whitelisted the FMV domains, the browser will silently block the script or iframe. Check your browser console (F12) for CSP violation errors.

How to check if you have a CSP

Open your browser’s developer tools (F12), go to the Network tab, reload the page, click on the main document request, and look for a Content-Security-Policy response header. If there isn’t one, you don’t need to do anything here.

Not sure if this applies?

Most small-to-medium business websites don’t have a CSP. If the Builder opens fine after installation, you can skip this page entirely.

Other security headers

These common security headers do not need any changes for the FMV widget: