Canonical Tag <link rel="canonical" href="your website"/> is mainly used for the purpose of avoiding page duplication issues. For example: The same page is opening for different URL's (your website, your website/index(.)html, your website/index(.)html-1, your website/index(.)html-2,...your website/index.html-99), you can use canonical tag to specify particular URL for search engine robots, bots or spiders to cache and index.