After the installation of the SSL certificate and forcing HTTPS protocol, the mixed content issue can appear on the website. This displays a "Not fully secure" warning next to the domain in the URL bar:
Mixed content means that you are trying to load images or other content with HTTP in their links. To fix this, edit all the links on your page to have HTTPS at the beginning instead.
If you are using the Elementor plugin, go to Elementor → Tools, and in the Replace URL page, insert your domain address with HTTP and HTTPS:
After this, the Mixed content issue will be fully resolved. If you don’t have Elementor, check the options below:
Method 1 - Install the Really Simple SSL Plugin
Log in to your WordPress dashboard and click on Plugins → Add New
Install and activate a plugin named Really Simple SSL. Then go to Settings → General:
And change the address of your blog from http:// to https://
Method 2 - Install the Better Search & Replace plugin
Install the plugin Better Search & Replace, then open Tools → Better Search Replace.
In the Search for field, enter the domain's name with HTTP. For example: http://domain-name.com
In the Replace with field, enter the domain's name with HTTPS. For example: https://domain-name.com
Tick Select all the tables, untick Dry Run, and press the button Do Search & Replace
Method 3 - Add Code to Your .htaccess File
If the first two steps didn’t help you, you can also open your public_html/.htaccess file (or create it if it wasn’t created yet) and insert the code below:
Header always set Content-Security-Policy: upgrade-insecure-requests
Save the changes and reload your website - it should already be working fully secured 💪
NOTE:
This option is not recommended if your website uses symlinks