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Sapling's AI detector comes from an NLP tooling company, not an integrity company, and it shows: a public API, per-sentence perplexity scores and a Chrome extension built for triage work. Its independent record is the widest we have reviewed, from zero false positives in Scribbr's test to a 90 percent false positive rate in a 2025 Texas A&M study. That volatility, not any single score, is the finding.
Winston AI advertises 99.98% accuracy, the highest self-claimed figure in the detector industry, measured on an internal test set the company has never published. The peer-reviewed RAID benchmark put its overall accuracy at 71% at a fixed 5% false positive rate, still second among the four commercial detectors tested. Here is what each number actually measures, and who this tool genuinely suits.
Scribbr's free AI checker posts the best free-tier numbers around: 78 percent accuracy, tied for first, in Scribbr's own published comparison, with the premium tier at 84 percent. The catch is the word "own": the test was designed, run, and graded by the vendor, and the other top free tool belongs to the same parent company. Here is what those numbers rest on, what the premium tier adds, and why a Scribbr pre-check cannot forecast a Turnitin result.
Copyleaks is the AI detector most students meet without choosing it, bundled with plagiarism checking inside Canvas, Moodle, and Blackboard. The vendor advertises over 99 percent accuracy and a .03 percent false positive rate. In the June 2026 Vrije Universiteit Brussel study, it failed to fully flag a single one of 40 entirely AI-generated papers. Here is what the evidence actually shows.
Pangram publishes a false positive rate of roughly 1 in 10,000, and unlike most detector vendors it now has recent independent research pointing in the same direction. A peer-reviewed 2026 study from Vrije Universiteit Brussel found it was the only tool of four that produced satisfactory results on master's level papers. Here is what the studies measured, where the evidence is still thin, and what no detector score can prove.
A submission system collects things in a fixed order, and the item that stops you is almost never the manuscript. This checklist follows the portal's own sequence, from the manuscript file through figures, competing interests, funding, data availability, author contributions, ORCID and suggested reviewers, to the cover letter as the last item on the list.