OpenCart Canonical URLs SEO extension
OpenCart is a great free, open source PHP cart software. Unfortunately it’s quite behind in terms of SEO. A default installation will end up flooding Google’s index with many duplicate category, index, product, and information pages which will diluting your site’s search ranking and incurring thin content penalties. Not to fear, this simple add-on will correct these shortcomings by adding canonical links to your category pages, your site’s main page, and all information pages (shipping, terms, about, etc). This plugin also fixes the bug in all versions of OpenCart which puts the wrong canonical URL in the products page canonical tag.