To resolve the mixed content issue on your WordPress site, follow these organized steps:

1. Add the Content-Security-Policy Header:

   • Open your .htaccess file.
   • Place the following header at the top of the file:

     Header set Content-Security-Policy "upgrade-insecure-requests" env=HTTPS
     

   • This instructs browsers to use secure links when accessed via HTTPS.

2. Update HTTP Links to HTTPS:

   • Use an SSL Checker tool to identify mixed content.
   • Manually update all HTTP links in your WordPress editor to HTTPS.
   • Ensure images and other resources are updated similarly.

3. Use Relative URLs for Secure Links:

   • Modify image tags and other resource links by adding a backslash before the filename, e.g., ‹img src="/image.gif"›.
   • This allows browsers to automatically use HTTPS if the connection is secure.

4. Handle Third-Party Content:

   • If content is linked from third-party sources, upload it to your server and update links to point to your secure URL.
   • Contact a web designer or hosting provider if you can't access these files directly.

5. Clear Browser Cache:

   • After making changes, clear your browser's cache to ensure updates are applied correctly.

6. Consider Using Plugins:

   • Install plugins like Really Simple SSL to automate SSL and mixed content management.

7. Test and Monitor:

   • Use tools like the SSL Checker to monitor progress.
   • Regularly test each change to ensure mixed content issues are resolved.