Hello,
Our intention is to install an SSL certificate on our website without making the switch from HTTP to HTTPS at this time.

We have a few questions regarding the installation process. First, will a duplicate of the HTTPS site be visible in search engines after the SSL certificate is installed? Second, will there be any issues with traffic or the issuance of the certificate? Finally, if the HTTPS site is only available through direct access, will our links, robots, sitemap, and Google Webmaster data remain the same?

If your website is hosted on a server, it should be accessible through HTTPS immediately. But if you are self-hosting your site, you can simply exclude the HTTPS section in nginx or apache.

What issues might arise from installing an SSL certificate only when it becomes necessary?

It is possible to host two different websites on the same domain over HTTP and HTTPS protocols. However, the Same Origin Policy considers different protocols as different enough to prohibit resource access without explicit permission. If the websites are completely different, it can confuse and make it difficult to use features like "raising" links to HTTPS (such as HSTS).

HTTP and HTTPS protocols use different ports by default, 80 and 443 respectively. DNS features require that the same machine serves both protocols, but within the machine, ports 80 and 443 can listen to two different processes configured differently. Although this is just a theory, I have not come across such a situation in practice.

In practice, you can create a configuration file in nginx with one block specifying "listen 80" and serving HTTP, and another block for "listen 443 ssl" and specifying settings for HTTPS.

Regarding your concern about a duplicate HTTPS site being visible in search engines after installing the SSL certificate, the answer is yes, it's possible. When you install an SSL certificate, it enables HTTPS on your site, and search engines like Google may crawl and index both the HTTP and HTTPS versions of your site. This can lead to duplicate content issues, where both versions of your site are visible in search engine results pages (SERPs). However, since you're not planning to switch to HTTPS at this time, you can avoid this issue by not allowing search engines to crawl the HTTPS version of your site. You can do this by adding a "noindex" meta tag to the HTTPS version of your site or by blocking search engines from crawling the HTTPS version in your site's robots.txt file.

Secondly, regarding potential issues with traffic or the issuance of the certificate, there shouldn't be any significant issues if you're not planning to switch to HTTPS at this time. The SSL certificate will be installed on your site, but since you won't be redirecting traffic to the HTTPS version, your site's traffic shouldn't be affected. However, keep in mind that some older browsers or devices may not support the SSL certificate, which could lead to errors or warnings when accessing the HTTPS version of your site. As for the issuance of the certificate, the process should be straightforward, and you shouldn't encounter any issues as long as you follow the certificate authority's instructions and provide the required information.

Regarding your question about links, robots, sitemap, and Google Webmaster data, since the HTTPS site is only available through direct access and not through search engines or redirects, these elements should remain unaffected. Your links will still point to the HTTP version of your site, and your robots.txt file and sitemap will continue to reference the HTTP version. Similarly, your Google Webmaster data will remain the same, as Google will still be crawling and indexing the HTTP version of your site. However, it's worth noting that if you decide to switch to HTTPS in the future, you'll need to update your links, robots.txt file, and sitemap to reference the HTTPS version, and you may need to verify the HTTPS version of your site in Google Webmaster Tools.