Redirect non-www to www in htaccess (in Wordpress multi-site)

Question

I'm having trouble redirecting non-www to www in htaccess.

The goal is to have non-www URLs (with or without subfolders) for a particular domain (domain1.co.uk) redirect to their www equivalents.

So:

'domain1.co.uk' should redirect to www.domain1.co.uk
and
'domain1.co.uk/subfolder' should redirect to www.domain1.co.uk/subfolder

I've tried a couple of things, each with undesired results.

Attempt #1:

RewriteCond %{HTTP_HOST} ^domain1.co.uk [NC]
RewriteRule ^(.*)$ www.domain1.co.uk/ [L,R=301]

Result #1: non-www URLs with subfolders redirect to the homepage (so it's impossible to access any subfolders without including 'www' in the URL)

Attempt #2:

RewriteCond %{HTTP_HOST} ^domain1.co.uk [NC]
RewriteRule ^(.*)$ www.domain1.co.uk/$1 [L,R=301]

Result #2:
'domain1.co.uk/subfolder' redirects to www.domain.co.uk/subfolder (as desired)
but 'domain1.co.uk' now redirects to www.domain.co.uk/www/ (strange result)

Any idea what might be happening here?

I'd be happy to post the full content of the .htaccess file if that would help.

Answer 1

To redirect non-www to www, you can use this :

RewriteEngine on

RewriteCond %{HTTP_HOST} !^www\. [NC]
RewriteRule ^ http://www.example.com%{REQUEST_URI} [L,NE,R=301]

Clear your browser cache before testing this.