Starting in 2014, Google began to emphasise on importance of making web more secure for every visitor. In 2017, their requests became more persistent, and finally in July 2018, the search giant began to notify the webmasters that the Chrome browser starting with version 68 will display a warning Not Secure for all HTTP pages.
1. Generate and configure a free SSL certificate on your server. In 2017, Google and other companies began to sponsor and advertise the free SSL certificates from Lets Encrypt to make switching from HTTP to HTTPS much easier. They are continuing to support it.
2. HTTP + HTTPS. Don't disable HTTP prior to HTTPS version will be fully checked, both of them should work while switching. Tech support should configure your web server so that you will get an A+ or an A rating on the SSL Labs test. Check whether everything works correct and fix the errors.
3. Change all website URLs to HTTPS. Then change links in HTML and CSS for images, styles, scripts and other files to HTTPS. Modern CMS do this automatically. If you’re using CDN ensure it supports SSL as well.
4. Meta-tag "referrer". This tag passes the referrer information when the visitor goes to the third-party website from yours. Especially, the use of this tag is useful for sites of webmasters who exchange traffic or want to track their visitors interactions deeper.
Place tag "referrer" in the head
of all website pages: meta name="referrer" content="origin"
As you can see on the graph, without this tag, after switching to HTTPS referrer data is lost.
6. Set up redirect. Force a 301 redirect for all website URLs on HTTPs.
7. Get your website on Google. Request indexing. Add a sitemap of your website to Search Console. Check for the crawl errors periodically.
If you’ve followed all these steps correctly your site should not have a long traffic drop. It is even might go up as it happened with our client’s website.