Full Definition
A canonical URL (declared via the HTML tag `<link rel='canonical' href='...' />`) is your way of telling Google: 'I know this content appears at multiple URLs, but this specific URL is the one I want you to index and rank.' Duplicate content is more common than most people realise. Your homepage might be accessible at: - `https://yoursite.com` - `https://yoursite.com/` - `https://www.yoursite.com` - `https://yoursite.com/index.html` From a user's perspective these are all the same page. But to Google's crawler, they can look like separate pages with identical content. Without canonical tags, Google has to guess which one to rank — and may split the ranking strength between all versions, weakening them all. E-commerce sites are particularly vulnerable because the same product can appear at multiple URLs due to filtering parameters (e.g., `?color=red&size=M`). A canonical tag on each of these variants pointing back to the main product page consolidates all the SEO value. Canonicals are also useful for content syndication — if you republish your blog post on Medium or LinkedIn, you can ask those platforms to add a canonical pointing back to your original post, ensuring Google credits you as the source. Actionable tip: Check your website right now. Go to your homepage and add `www.` to the URL if it's not there, then check if you're redirected or if both versions load. If both load, you likely have a canonicalisation problem worth fixing.