Canonical tag
A canonical tag is an HTML link element, written as rel="canonical", that tells search engines which URL is the preferred version of a page when several URLs show the same or very similar content. It helps consolidate ranking signals onto one address.
A canonical tag is a line of HTML placed in the head of a web page that points to the URL the site owner wants search engines to treat as the main version. The attribute is written as rel="canonical" and looks like a link element with the preferred address in its href. It is a hint rather than a command, so search engines weigh it alongside other signals such as internal links, redirects, and sitemaps before deciding which version to index.
Duplicate content shows up more often than most business owners expect. A single product or service page might be reachable with and without a trailing slash, through http and https, with tracking parameters appended to the end of the address, or through a print-friendly copy. Each of those addresses can be crawled as a separate page. When the content is the same, search engines have to choose one, and the choice may not match what the business wants to rank. A canonical tag removes that guesswork by naming the preferred URL on every duplicate.
The main reason it matters is that links and ranking signals get split across duplicates when no preferred version is declared. Pointing the canonical tag at one address helps concentrate those signals there. This matters for e-commerce catalogues, multi-location service pages, and content management systems that generate several paths to the same article, all of which are common among Malaysian businesses running sites on WordPress or WooCommerce.
A canonical tag is one of the more routine tasks in technical SEO, and it sits alongside redirects and crawl settings as part of keeping a site's index clean.