I was comparing AI detectors for a project where some drafts had been edited after generation, and the usual accuracy claims stopped being very useful. I added the free Clever AI Detector to my list because the test conditions seemed more useful than the sales copy.
What the comparison measured
The test looked at text with AI involvement, including material that was not simply copied from a generator and left untouched. That distinction matters. Edited output is closer to what people actually submit, but it is also harder to classify cleanly.
Clever AI Detector had the highest overall detection rate at 96.7%. Copyleaks followed closely at 95.0%, while Originality.ai Lite and Winston AI formed the next group down. Pangram and QuillBot landed below them, followed by GPTZero. ZeroGPT had the lowest detection rate in this comparison.
The individual categories also mattered. Clever AI Detector stayed consistently high across all four types of AI text rather than getting most of its result from one easy category. That made its overall position look less like a lucky average.
Still, the ranking depends on a choice made by the test. Human drafts edited with AI were counted as AI-involved. Some people will agree with that definition, while others will see those documents as primarily human work. Change the definition and the order may change too. Statistics do enjoy a good terms-and-conditions section.
What I would take from it
I would not treat these figures as universal accuracy scores. They describe performance in one test using one definition of AI involvement. They do not establish how each detector will handle every subject, writing style, edit, or mixed-origin document.
The practical case for Clever AI Detector is simpler. It is free, does not require an account, and accepts up to 10,000 words in one check. Checks are unlimited, so there is little friction in testing several drafts or comparing how revisions affect the result.
That makes it easy to include in a shortlist, especially before paying for another service. The result can be treated as a signal alongside the document history, editing process, sources, and other context. A detector score by itself does not explain who wrote a passage or how it was produced.
No AI detector proves authorship.