GPTZero vs Copyleaks vs Originality: AI Detector Accuracy Comparison

Sep 25, 2025 · 8 min read

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Being able to tell if a document has been written by AI (or not) has become more essential, while also becoming trickier, as generative AI only becomes more sophisticated. Plus, AI detection is always shifting, as what worked a few months ago might quickly have become outdated. This inevitably leads to asking: what is the most accurate AI detector?

After all, what never changes is the importance of accuracy. But with so many options out there, what are the best AI detectors to choose from? In this post, we compare GPTZero, Copyleaks, and Originality.AI to see which one is the most reliable AI detector right now, and answer common questions around accuracy.

TL;DR

We compared GPTZero, Copyleaks, and Originality across 3,000 samples of human-written and AI-generated text from a variety of sources, including essays, research papers, blog posts, and creative writing.
GPTZero came out as the leader, with 99.3% overall accuracy and a false positive rate of just 0.24%. It’s far less likely to wrongly accuse a student of AI use and can still detect the latest AI models such as GPT-5, Gemini 2.5, and Claude Sonnet.
Copyleaks performed well on certain tasks but misclassified about 1 in 20 human-written documents, a rate too high for most classrooms or editorial settings.
Originality is very strict and sensitive, which can be useful in niche workflows, but it struggles with newer AI models.

Benchmarking AI Detector Accuracy

In recent blog posts, we’ve described how we are constantly evolving GPTZero’s AI detector. Our major detector updates demonstrate our improved performance on the latest and most popular language models used by students and writers, including GPT5. We wanted to compare our performance to other AI detectors, starting with Copyleaks and Originality.

For this benchmark, we tested 3,000 samples with half written by humans, half by AI. The texts were from a wide range of real-world sources: student essays, academic papers, textbooks, news articles, blog posts, and even creative writing, showing us how each detector performs in everyday scenarios.

AI Detector	Accuracy	False Positive Rate	Recall
GPTZero	99.3%	0.24%	98.8%
CopyLeaks	90.7%	5.26%	86.9%
Originality	83.0%	4.79%	70.8%

Table 1: Overall accuracy, false positive rate, and recall of popular AI detectors

When comparing, there are three numbers we prioritize: accuracy, which shows how often the tool got it right overall, false positives (which show us often genuine human writing was wrongly flagged as AI), and recall (which indicates how often the tool successfully spotted AI-generated text). All together, these can illustrate the extent to which a detector can be relied upon as well as whether it is fair.

We also report recall by the language model that was used to generate the AI documents, so you’ll know what to expect when you scan text generated by your go-to tool. These results are shown in Table 2.

Language model	GPTZero recall	Copyleaks recall	Originality recall
GPT5	100.0%	47.5%	31.7%
GPT5-mini	94.9%	18.0%	7.3%
GPT5-nano	99.0%	64.1%	48.3%
GPT4.1	99.1%	55.7%	67.7%
GPT4.1-mini	100.0%	77.7%	90.4%
GPT4o	99.1%	73.4%	97.7%
GPT4o-mini	98.3%	77.2%	98.6%
o3	96.3%	45.4%	7.6%
o3-mini	97.4%	75.0%	94.2%
Gemini-2.5-pro	95.8%	59.7%	78.2%
Gemini-2.5-flash	96.5%	63.5%	87.5%
Gemini-2.5-flash-lite	98.7%	76.0%	99.1%
Gemini-2.0-flash	93.8%	69.6%	90.4%
Claude Sonnet 4	99.0%	74.0%	95.1%
Claude Sonnet 3.7	97.3%	68.1%	77.8%

Table 2: Recall by language model

GPTZero vs. Originality.ai

Our benchmark shows that GPTZero outperforms Originality in both accuracy and recall, especially when detecting text generated by the newest and most advanced AI models.

Across 3,000 test samples, GPTZero achieved 99.3% overall accuracy, compared to 83.0% for Originality.

That’s a gap of over sixteen percentage points, more than enough to make a tangible difference when these tools are used in classrooms. Essentially this shows that GPTZero is much more reliable when identifying if a piece of text was written by a human or an AI.

When it comes to false positives, GPTZero’s false positive rate was 0.24% (about one in every 400 documents), while Originality’s was 4.79% (roughly one in twenty). Both are much better than the industry average, but the difference matters a lot, especially when applied to larger groups. For educators with big classes, even a small increase in false positives can translate to many more students wrongly flagged for AI use, which can be damaging.

Where GPTZero really shines is recall, or the ability to catch AI-generated text. This becomes especially important as students and writers gain access to more advanced tools like GPT-5, Gemini 2.5, and Claude Sonnet. In our breakdown by model, GPTZero consistently led the pack.

For example:

GPTZero caught 100% of GPT-5 text, while Originality flagged just 31.7%.
On GPT-5 mini, GPTZero’s recall was 94.9%, while Originality managed only 7.3%.
Even on older models like GPT-4.1, GPTZero’s recall remained strong at 99.1%, compared to Originality’s 67.7%.

Originality does have strengths, particularly its strictness and sensitivity. Some value this ultra-cautious approach, and in contexts such as legal documents, a stricter tool can be useful. But this can also bring potentially unnecessary friction in everyday situations. Originality’s interface is also more rigid with a reporting style that can feel less intuitive.

In independent testing by Tamzid Ahmed, his review found Originality failed to detect plagiarism in live content. In his test, he scanned a page published two weeks earlier on TechRadar, and while the page had already been indexed by Google and therefore was publicly accessible, Originality did not recognize it as plagiarized. This shows Originality may struggle to scan and cross-check live web data.

GPTZero, on the other hand, was able to identify the plagiarized content, making it more reliable for those who need AI detection and plagiarism in the same workflow. On top of this, GPTZero also comes with authorship verification tools like Writing Replay, where teachers can see a document unfold in real time and see exactly who contributed what. This combination of features is part of what makes GPTZero a particularly great fit for educational institutions.

GPTZero vs. Copyleaks

We found GPTZero outperforms Copyleaks when it comes to both accuracy and false positive rates. GPTZero achieved an overall accuracy of 99.3%, while Copyleaks came in at 90.7%. For the false positive rate, GPTZero’s was 0.24%, as in, roughly one in 400 human-written documents might be incorrectly flagged as AI-generated. Meanwhile, the false positive rate we computed for the Copyleaks detector means it will misclassify 1 in 20 human-written documents as AI.

For a teacher with a class of 200 students, that is huge: it could mean ten wrongful accusations instead of just one or two. False positives have a very real human cost (in the worst cases it can cause lasting harm to a student's academic record or emotional wellbeing.)

Copyleaks offers tools designed to fit into institutional systems, including options for plagiarism detection and LMS integrations, and for some schools, this level of infrastructure is appealing. But these features don’t offset the risks of higher misclassification rates. In independent testing, Copyleaks showed uneven performance, with accuracy dropping when content was paraphrased using tools like QuillBot: out of 10 AI paraphrased texts, CopyLeaks detected only six of them accurately (and misclassified 4), meaning its overall Accuracy Rate for AI Paraphrased Content was 60% for that exercise.

For user experience, Copyleaks’ dashboard can be a steeper learning curve for teachers new to AI detection. GPTZero, on the other hand, has reporting that is straightforward, and the Writing Replay feature gives educators a genuine peek through the window of a student’s process so that teachers may understand it better.

Other Factors to Consider

As mentioned, a key consideration is the complementary tools alongside detection, and GPTZero’s plagiarism scanning as well as Writing Replay helps educators understand how a piece of writing came together, instead of relying solely on a static result. Copyleaks and Originality offer some extra features too, but the depth and clarity are mixed, especially when it comes to side-by-side analysis or transparent reporting.

Integration, and the ease of such, also counts, as many institutions now rely on learning management systems (LMS) like Canvas or Blackboard along with plagiarism checkers. If an AI detector doesn’t integrate smoothly through an API, it creates extra steps for teachers and students, which can lead to confusion or inconsistent use: with this in mind, GPTZero’s API is designed to be super simple to connect into existing workflows.

Support and training matter, and rolling out AI detection across a department or university isn’t about handing teachers a login screen and a PDF. Faculty need clear guidance on how to interpret results and handle difficult situations with students. GPTZero works closely with schools and teachers to provide this support, including a very popular webinar series. Copyleaks and Originality.ai might focus on the software but offer limited hands-on help.

Finally, usability: a tool can have the most advanced detection models ever, but if the interface feels like a maze, the user experience won’t be great. GPTZero’s dashboard is intentionally designed to be clean and intuitive, giving educators an easy view of what’s been flagged and why. Copyleaks and Originality offer similar functionality, but user feedback often points to a longer learning curve because of more complicated workflows.

Limitations & ethical considerations

Should We Even Use AI Detection Tools?

AI detectors aren’t perfect, and the goal shouldn’t be to “catch” students out. One of the biggest risks comes from false positives, which can have very real consequences, and at a broader institutional level, universities risk legal challenges and reputational harm if too many wrongful accusations occur.

False negatives cause a different kind of issue, as it’s frustrating (and demoralizing) for students who follow the rules to see others get away with submitting work they didn’t write. It also undermines trust in the system. False negatives are especially common when AI writing has been mixed with paraphrasing tools like QuillBot to rewrite AI text. Detectors need to be regularly updated to keep up with the newest language models. Without those updates, a massive amount of AI-generated work can go unnoticed.

This is why human review is essential: no matter how advanced the software, a machine should never have the final word, and the best systems combine detection tools with context. A flagged paper is the start of a conversation, and actually taking the time to talk with the student will always provide a more holistic picture than any algorithm. As mathematics teacher Humayra Mostafa has shared with GPTZero, “I believe communication is important between the teachers and the students so that students understand the goals and intentions of learning.”

Humayra Mostafa (left) and a view of her classroom (right)

Conclusion

Our benchmark shows GPTZero delivers the highest overall accuracy with a false positive rate well below the industry standard, outperforming both Copyleaks and Originality on the latest models like GPT-5 and Gemini 2.5. Basically, GPTZero is much less likely to misclassify human work while still catching AI-generated text at scale.

Copyleaks and Originality have their strengths, but Copyleaks has higher rates of false positives, creating real risks for students; while Originality’s strictness can be useful in certain workflows, but it often comes at the cost of accessibility.

Among the tools we tested, GPTZero came out on top, but it also treats AI detection as only one part of the puzzle. GPTZero is designed to support human judgment, giving teachers and institutions the context they need to have informed conversations about academic integrity. Scan your document for AI detection and see for yourself.