A canonical URL is the preferred version of a webpage that search engines should index. It’s used to avoid duplicate content issues, which can arise when the same content is accessible through multiple URLs.
For example, your site might display the same content at both example.com/page and example.com/page?ref=123. A canonical tag tells search engines which version to prioritize, consolidating ranking signals and preventing dilution.
Yes, you need canonical URLs if your site has duplicate or similar content across multiple pages. They ensure that search engines focus on the most relevant version, improving your SEO and avoiding penalties for duplication.