I was wondering which forum softwares have a canonical plugin or add on? I just created one for mybb: http://www.mybbcentral.com/thread-2644.html It's very comprehensive and works with the built-in SEF (enabled or disabled) setting of mybb. For SMF there is this: http://custom.simplemachines.org/mods/index.php?mod=1644 However I don't think that's a very good mod as it doesn't take care of all the possible pages in the forums or threads that might occur. So it misses the mark. It also doesn't appear to work with their built-in sef urls. For VB I see this: http://www.vbulletin.org/forum/showthread.php?t=205512 That looks okay but again not comprehensive imho. It won't correct a URL like this: http://forums.digitalpoint.com/showthread.php?p=6004397#post6004397 While mine for Mybb would. Using canonical is far more effective than altering all the links that something like VBseo tries to do. Now you don't have to alter links or how content is viewed by guests for SEO. You can use canonical. For more about canonical from Google, Yahoo, and MSN read their blogs: http://www.mattcutts.com/blog/seo-advice-url-canonicalization/ http://blogs.msdn.com/webmaster/arc...g-to-help-solve-duplicate-content-issues.aspx http://ysearchblog.com/2009/02/12/fighting-duplication-adding-more-arrows-to-your-quiver/ A good caconical tag, sef urls, and a proper robots.txt and you're pretty much SEO ready.