These rules are intended to be used in .htaccess files, as a RewriteRule in a *:80 VirtualHost entry needs no Conditions.
RewriteEngine on
RewriteCond %{HTTPS} off [OR]
RewriteCond %{HTTP:X-Forwarded-Proto} !https
RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R=301,L]
Eplanations:
RewriteEngine on
==> enable the engine at all
RewriteCond %{HTTPS} off [OR]
==> match on non-https connections, or (not setting [OR] would cause an implicit AND !)
RewriteCond %{HTTP:X-Forwarded-Proto} !https
==> match on forwarded connections (proxy, loadbalancer, etc.) without https
RewriteRule ^/(.*) https://%{HTTP_HOST}/$1 [NC,R=301,L]
==> if one of both Conditions match, do the rewrite of the whole URL, sending a 301 to have this 'learned' by the client (some do, some don't) and the L for the last rule.
nginx
server {
listen 80 default_server;
listen [::]:80 default_server;
server_name _;
return 301 https://$host$request_uri;
}