Occasionally, I feel like a blog post that I've written here on Codepunk has enough crossover reach that I contemplate cross-posting it on other platforms. A lot of times, I'm discouraged from doing that because of the golden search engine rule of not creating duplicate content. It has a net negative on your search engine rankings.
There is actually a little known HTML attribute value that allows you to distinguish duplicate content, and by doing so, instruct search engines that links to one particular URL, really should be noted as links to an originating URL. This attribute is the
A canonical URL is essentially a "preferred" URL, and by virtue of using it as the "originating" URL, you can increase your search rankings for the original URL by using it. Most importantly, however, is that by using it, you won't hurt your current search rankings for having duplicate content out there. Of course, this assumes that the platform you are cross-posting to allows for canonical URLs.
Setting a canonical URL is easy. You set it in the header of the page that carriers the duplicate information.
<link rel="canonical" href="http://example.com/original-post.html" />
Google has a great help page on the importance of canonical URLs to their search engine, and other methods for defining which pages are canonical.