Let's Encrypt- can we use a single redirect for multiple domains?

can you provide an example of how to accomplish this?

You have to do exactly what you described in your question.

Create a PHP type of application, named for example redirect_to_https and only add the .htaccess file with the following lines:

RewriteEngine On

RewriteCond %{HTTPS} off

RewriteCond %{REQUEST_URI} !^/(.well-known)(/|$)

RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}

Then create an http website, add all the domains and subdomains you want to redirect to https and only attach the application you've created above.

Every http request of a domain or subdomain on the list will be redirected to the exact same https url.

thanks. it seems to work for one site but not the other.

do i need to enable Lets Encrypt for each site that i will be redirecting via redirect_to_https app?

Let's Encrypt challenges happen over http. We added that condition in our documentation to make sure that requests for any .well-known/ urls do not get redirected to https, that might make the validation to fail.

The .well-known directory is an internet standard used for information discovery. The acme-challenge is specific to Let's Encrypt. Other ssl issuers use similar technics, to different directories, to verify domains.

The .well-known directory is also used by other services, most commonly caldav clients that use it to discover calendars on a calendar server.

Yes, that should be added to your redirect application as well. Just above the ReWrite rule as shown in our documentation here