Content at Scale's free AI detector was folded into the company's 2024 rebrand to BrandWell, and the tool now lives under the BrandWell name. It reports an overall human-likelihood score with passage-level breakdowns and remains free to use up to a word limit.
AI content detectors
A directory of tools that estimate whether text was AI-generated.
AI detectors estimate the probability that a passage was written by an AI model. They are the tools that humanizers are measured against. Detection is probabilistic; see the research for what that means.
Copyleaks began as a plagiarism-detection service and added an AI-content detector that reports whether text is likely human- or AI-written, with language coverage beyond English. It is used by educators, publishers, and enterprises, and offers an API alongside its web tool.
One of the earliest and most widely used AI-text detectors, popular in education. Uses perplexity- and burstiness-style signals plus newer models. Accessible free tier; accuracy varies with text length and editing.
A paid detector aimed at publishers, agencies, and SEO teams, known for aggressive detection and a plagiarism checker. Often the hardest detector for humanizers to beat, at the cost of more false positives.
QuillBot's AI detector is a free tool, separate from its well-known paraphraser, that estimates whether text was AI-generated. It requires no signup for checks below a word limit and shares detection technology with the Scribbr detector under the same parent company.
Sapling offers a free web-based AI-content detector alongside its business writing-assistant products, returning an overall AI-likelihood score with color-coded sentence highlights. An API is available for teams that want to integrate detection programmatically.
Scribbr offers a free AI detector aimed at students and academic writers, returning an AI-likelihood estimate for pasted text. Scribbr and QuillBot are both owned by Learneo, and the detector runs on QuillBot's detection technology.
Turnitin adds AI-writing detection to its long-established plagiarism and academic-integrity platform, surfacing an estimated percentage of a submission likely to be AI-generated. It is aimed at schools and universities and is delivered inside institutional licenses rather than as a standalone consumer tool.
Winston AI is a subscription detector that reports a likelihood score for AI-generated text and produces shareable PDF reports, with plagiarism checking and OCR among its features. It targets educators, writers, and publishers who want documented results.
Writer.com offered a free, no-login AI content detector that checked pasted text or a URL and returned a simple human-percentage score. Writer discontinued the detector on December 22, 2025, including the free tool and its legacy API, as the company refocused on its enterprise AI platform.
ZeroGPT is a free, ad-supported AI-text detector that returns a percentage estimate of AI involvement and highlights suspected sentences. Its accessibility makes it a common first stop for casual users, students, and writers, with paid tiers adding higher limits and reports.
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