PaperOK duplicate checking system has two options: paid version and free version. The free version provides a certain number of free duplicate checks, but after a certain number, you need to pay. The paid version provides more duplicate checking times and more comprehensive testing services. The specific charging situation also needs to be determined according to the needs of users and the selected services.

Different duplicate checking systems have different algorithms and databases, so the duplicate checking results will be different. For the first draft of the paper, it is suggested that the paper series free duplicate checking software such as paperfree, papertime and paperday can be used for testing, and for the final draft, the duplicate checking system required by the school can be used for testing. Ensure the accuracy and effectiveness of duplicate checking.