Rewrite condition for domain.com to www.domain.com using HTACCESS

Redirecting from domain.com to www.domain.com is mostly helpful as part of SEO. The rule for rewriting the site is shown below.

rewritecond %{http_host} ^domain.com [nc]
rewriterule ^(.*)$ http://www.domain.com/$1 [r=301,nc]

Just change the domain name to your site name to use the rewrite rule.