If you want to check the copy for free, here are some possible options:

1 Use academic search engines: Academic search engines can provide free duplicate checking services, such as Google Academic Search and Baidu Academic. These search engines will provide relevant academic papers and materials, and help you find free duplicate search websites.

2 Use free duplicate checking websites: There are some free duplicate checking websites available, such as paperfree, papertime, paperYY, etc. These websites usually provide a certain amount of free duplicate checking, but it should be noted that due to its free nature, the duplicate checking results may not be completely accurate and need to be carefully screened.

3. Ask for free duplicate checking discount: Some duplicate checking websites will provide free duplicate checking discount activities, such as HowNet duplicate checking and Wanfang duplicate checking. These preferential activities usually need to meet certain conditions, such as new user registration, sharing invitation code and so on.