QuillBot offers a free plan. It allows you to use their paraphrasing tool, but it comes with a character limit and fewer rewriting modes. To remove these limitations, you'll need to upgrade to a paid subscription.
QuillBot's paraphrasing usually does simple synonym replacement and sentence restructuring. If you need a rewriter that can do more than just that and make your AI-generated text undetectable to AI detectors, then this tool won't be enough.
Instead, we suggest you try Humbot. It's a powerful AI humanizer that can humanize text generated by any AI, and help you pass the detection of Originality, Turnitin, GPTZero, and many other stringent AI detectors.