In most sites, a lot of links are saved into the content, pluginoptions or even worse, in the theme. When you switch to ssl , these are still http, instead of https. To ensure a smooth transition, this plugin auto replaces all these links. If you see in the scan results that you have fixed most of these links, you can try to run your site without this replace script, which will give you a small performance advantage. If you do not have a lot of reported insecure links, you can try this. If you encounter mixed content warnings, just switch it back on. <br><br><b>How to check for mixed content?</b><br>Go to the the front end of your website, and click on the lock in your browser's address bar. When you have mixed content, this lock is not closed, or has a red cross over it.