Is your website able to be accessed via https? Is there a redirect from http to https or vice versa? If https is enabled, there should be a 301 redirect from the http to https version of your domain.
The redirect check tool looks at a number of different URLs for your homepage, and reports back on the response code given by each. It then suggests the apache htaccess code to correct the issue.
To be completely safe, a 200 response should only be returned by one page. Other pages should return a 404 or 301. Anything else could be a potential duplicate content problem.
This tool was updated on the 26th of October, 2016 to work with https URLs.
Karl, Senior Account Manager of KIWIreviews.co.nz
Just wanted to say a quick "Thanks!" for the redirect check. Awesome tool, well worth using. Great that it feeds back code snippets for direct copy'n'paste, saving time and hassle. Perfect for helping weak programmers to get strong results. (Welcome to quote me on that if you like. ;) )