https://www.danielmorell.com/guides/htaccess-seo/sample-code/redirect-sample-code
tl;dr
.htaccess for www.
(www maybe better when needing to use a CNAME to point to a load balancer domain, this approach is used by Google.com, Odoo.com enterprise etc)
#### Force HTTPS
#### Force WWW
#### Remove trailing / from file
# Turn on Rewrite Engine
RewriteEngine On
# Remove trailing slash from non-filepath urls
RewriteCond %{REQUEST_URI} /(.+)/$
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ https://www.example.com/%1 [R=301,L]
# Include trailing slash on directory
RewriteCond %{REQUEST_URI} !(.+)/$
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^(.+)$ https://www.example.com/$1/ [R=301,L]
# Force HTTPS and WWW
RewriteCond %{HTTP_HOST} !^www\.(.*)$ [OR,NC]
RewriteCond %{https} off
RewriteRule ^(.*)$ https://www.example.com/$1 [R=301,L]
.htaccess for root domain
(my preferred, simpler but could be more restrictive for enterprise scaling)
#### Force HTTPS
#### Remove WWW
#### Remove trailing / from file
# Turn on Rewrite Engine
RewriteEngine On
# Remove trailing slash from non-filepath urls
RewriteCond %{REQUEST_URI} /(.+)/$
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^ https://example.com/%1 [R=301,L]
# Include trailing slash on directory
RewriteCond %{REQUEST_URI} !(.+)/$
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^(.+)$ https://example.com/$1/ [R=301,L]
# Force HTTPS and remove WWW
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [OR,NC]
RewriteCond %{https} off
RewriteRule ^(.*)$ https://example.com/$1 [R=301,L]
