Nowadays, there are more and more paper duplicate checking systems on the market, both paid and free. For example, the duplicate checking system of HowNet is well studied, well known and has many consumer groups. Of course, there are also free papers, but there are also some paper duplicate checking systems. As long as you pay attention to the official account of WeChat, you can get the duplicate checking words for free. The official WeChat account provides free paper duplicate checking systems such as paperfree, paperday and papertime. You can directly import files into your mobile phone for duplicate checking, which is convenient and quick, and is very popular.