Duplicate content refers to significant portions of identical or very similar text that appear on more than one web page, either within a domain or across domains. Duplicate content is considered problematic for SEO because search engines avoid including similar web pages in search results, as they compromise user experience.
However, according to Matt Cutts, duplicate content won't hurt your site's SEO unless it is "spammy." If you're concerned about duplicate content on your site, review the following best practices:
- Use 301 redirects to redirect traffic from old or retired URLs to new URLs.
- If there are pages on your site with duplicate content that you don't want to appear in search results, use the noindex tag to deindex them.
- If there are multiple versions of a page with very similar content, use canonicalization to tell Google which version is the "canonical" URL.
- Consider consolidating similar pages rather than hosting multiple pages with very similar content.