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:
Learn more about what to do about duplicate content in this guide or from Google’s webmaster guidelines.