Migrating your website to HTTPS may seem like a simple task. Get the TLS/SSL certificate, install it on your web server, and you’re done.
The real pain for large projects, however, is changing http:// resources to https://. These resources include images, videos, sounds, forms, scripts, and CSS files, along with any externally loaded third-party elements like tracking, ads, and widgets.
If an HTTPS page includes any of these elements served over the HTTP protocol, they are passed unencrypted from your web server to a visitor’s browser.