The latest version of Chrome (version 68) will now mark all HTTP sites as “not secure.” Up to this point, only a subset of HTTP pages was marked as “not secure” in the browser. Google intentionally made the transition a slow one in order to give developers plenty of time to move their sites over to a secure connection.
In terms of the number of sites affected by this, Google had shared some numbers earlier this year. According to the company, 81 of the top 100 sites on the Web now use HTTPS by default. It added that more than 68 percent of Chrome traffic on both Android and Windows and over 78 percent of Chrome traffic on Chrome OS and macOS now flows over HTTPS.
Google Chrome also offers a policy to control this warning on your domain.
chrome not secure