Flex Fields

Flex SSL is a lightweight WordPress plugin designed to secure your website by enforcing HTTPS across your entire site. Key features include:
<ul>
<li>Force HTTPS: Automatically redirect all HTTP requests to HTTPS.</li>
<li>Auto-Update URLs: Change WordPress site and home URLs from HTTP to HTTPS.</li>
<li>Cloudflare/Proxy Support: Detects HTTPS headers from Cloudflare or other reverse proxies to avoid redirect loops.</li>
<li>Security Headers: Optionally add HSTS, X-Frame-Options, X-XSS-Protection, and other security headers.</li>
<li>Mixed Content Fixer: Automatically correct HTTP links in your content to prevent browser warnings.</li>
<li>SSL Status: View current SSL status and certificate expiry date.</li>
<li>Redirect Options: Choose between 301 (permanent) and 302 (temporary) redirects.</li>
<li>Logs & Reports: Monitor changes and events in a log system.</li>
<li>Let’s Encrypt Integration (Coming Soon): Plan to automatically generate and renew SSL certificates.</li>
</ul>
<h3>License</h3>
Flex SSL is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version.
For more details, see https://www.gnu.org/licenses/gpl-2.0.html.

Flex SSL

Enables SSL & forces HTTPS on WordPress, updating URLs & adding security headers. Supports reverse proxies & soon integrates Let's Encrypt.

Stefan Kittel

It easily solves the problem of mixed unsafe content.
Once a web page has its contents, such as CSS, JavaScript or graphics loads unencrypted, the browser reports the whole website as unsafe.
This message will appear with this or similar texts “Connection is not secure” and “Parts of this page are not secure. This can e.g. be graphics. “.
Now you can check and correct all posts, comments, plugins and the theme …
Or you simply install “SSL Fixit”. 
Finished. There is nothing to configure.
The plugin simply replaces all http: // in the output with https: //.
However, if you still need unencrypted links, you can not use this plugin. 
But that should / should be there in the meantime only in exceptional cases.

SSL Fixit Plugin for WordPress by Stefan Kittel

A simple plugin to fix the html unsecure mixed content error

Flex SSL vs SSL Fixit Plugin for WordPress by Stefan Kittel