There's no such thing as a completely free service that can do a perfect job of plagiarism detection.
Here's why:
* Complexity: Detecting plagiarism is a complex task requiring advanced algorithms and massive databases. These resources aren't free to maintain.
* Accuracy: Free tools often have limitations in terms of accuracy, especially with paraphrasing and reworded content.
* Limited Features: Free options might have fewer features, such as word count limits or fewer checks per month.
However, here are some options that offer free versions with limitations or free trials:
* Grammarly: Their free version provides basic plagiarism checks.
* SmallSEOTools: Offers a limited free plagiarism checker.
* PaperRater: Offers a free version with a word count limit.
* Quetext: Provides a free trial period.
* DupliChecker: Offers a free version with limited checks.
Keep in mind:
* These free services are generally okay for quick checks but don't rely on them for serious academic or professional work.
* Consider using a combination of tools for more thorough checks.
* For accurate and comprehensive plagiarism detection, you might need to invest in a paid service.
Remember: Plagiarism is a serious academic and professional offense. Always strive to create original work and cite your sources properly.