Do you want to move a XenForo forum from a subdomain (like say forum.yourdomain.com) to the root domain (yourdomain.com)? The process is fairly simple and easy to follow. Here is a complete step by step guide.
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How to Properly Move XenForo to a New Domain Without Losing SEO
A complete step by step guide to properly move a XenForo forum from an olddomain.com to newdomain.com without having any significant impact of SEO.