When building websites, people are often concerned about not duplicating content across pages or sites. While there is no specific penalty for that, if Google thinks your website has the same content as another site, one of you won’t have a chance in the rankings.
So what does that mean for website themes and templates? If you use a popular one, are you at risk of facing duplicate content issues? In a word, no.
When Google looks at your content, whether it’s comparing it to others or just viewing the quality of it by itself, they’re looking almost exclusively at the actual text that you put on pages. The theme wrapped around it is just for show, and Google is well aware that many sites use the same theme as one another.
In a recent question posed to Google’s John Mueller (via SE Roundtable), a user asked “I create a WordPress theme and can I use it on multiple websites?”. John’s answer was clear, saying that “lots of sites use the same themes”.
Creating clear, concise, and valuable content is wildly important for your status online. Choosing the wrong WordPress theme could potentially cause speed or security issues, but Google won’t care a bit when it comes to content.