My suggestion is: use the same standard .htaccess configuration for WordPress on a single domain in each WordPress directory.
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
Along with it, add a small CODE to make sure users are redirected to the correct domain in case they reach to that subdirectory using another domain:
RewriteCond %{HTTP_HOST} !^domain\.com$
RewriteRule ^(.*)$ "https://domain.com/$1" [R=301,L]
After that, your .htaccess for domain.com will be like:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} !^domain\.com$
RewriteRule ^(.*)$ "https://domain.com/$1" [R=301,L]
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
and for subdomain.domain.com, it’ll be like:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} !^subdomain\.domain\.com$
RewriteRule ^(.*)$ "https://subdomain.domain.com/$1" [R=301,L]
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
Reasons:
-
Using standard CODE is recommended because it’s easier to maintain & debug, as it’s same everywhere.
-
The extra two line are recommended mainly for
SEO. Without them, one of your domain may be accessible using another domain. That may raise some duplicate content question.