9 Best Free AI Detectors for Teachers in 2024 (Recommended by Teachers & Professionals)

Educators’ nightmare started since the advent of ChatGPT, Bing AI, Google Bard and many other AI writing tools. This is because it implies the long-standing plagiarism checking system in schools and institutions has crumbled overnight under the weight of a new menace –  potential undetectable plagiarism. The need to detect plagiarism among student work is to maintain academic integrity and honesty, as well as promote originality of thoughts for intellectual growth. 

The good news is, in response to this escalating challenge, a myriad AI detectors have swiftly emerged to mitigate the problem. And we will be reviewing the best AI detectors for teachers in this article.  

However, the bad news is that the existence of AI detectors does not mean the end of educators’ nightmare. This is because while there are many AI detectors to help detect AI-generated content, there are also many AI tools being developed for the sole purpose to fool these AI detectors.  

Therefore, provide support to all our educator readers, we will not only be sharing with you the best FREE AI detectors in 2024 (our teachers community has tested these tools), but also equip you with knowledge on how AI detectors work, so you can know the right way to incorporate a much-needed layer of human proof to your students’ work while using these AI detectors. Let’s get started.

How Do AI Detectors Work?

AI tools and chatbots use natural language processing (NLP) techniques and algorithms to generate human-like responses based on the input. In other words, NLP informs machines the linguistic rules and contexts used in human language so they can interpret human language the way we do. As compared to how AI tools generate text, AI detectors use reverse engineering methods to identify NLP patterns and techniques commonly used to generate AI content.

And the main methods used by AI detectors are:

• Classifiers: Classifiers are machine learning models trained to classify data into predefined classes. Classifiers can be trained with labelled data, such as examples that have already been labelled as AI-generated or human-written. After they are trained, classifiers can identify language patterns such as how words, style, grammar and tone work together in a text. In general, human-written text tends to be more versatile, unpredictable, idiosyncratic and less perfect. 
• Embeddings: Embeddings are codes and vector representations used to measure the meaning of the words and how they are related to each other. In human-written text, the codes for similar or related words are typically located in close proximity. However, in AI-generated text, these codes may not be as closely grouped since the AI lacks a full understanding of the relationships between those words. 
• Perplexity: Perplexity is a measure randomness, uncertainty or complexity of a given text. Here is an example sentence: “ClassPoint is a PowerPoint teaching…” For a language model with high perplexity, it would propose “journey”, “delight” as answers. It is less predictable. For a language model with low perplexity, it would propose “tool”, “software” as answers. A sentence with higher perplexity is more likely to be human content.
• Burstiness: Burstiness is a measure of predictability in terms of sentence structure, through the variance of a sentence in terms of length, structure and tempo. A person writes in bursts when there is high variance in the sentence length, structure and tempo. And a paragraph with higher bursts is more likely to be human content.

These are methods AI detectors commonly used to detect AI-generated text. However, they are not fool-proof as students can bypass these detectors through paraphrasing AI-generated text, using various prompts to get AI writing tools to produce more “humanlike” content, and the easiest way of all, using tools the claim to get around AI detectors like Undetectable and Quillbot.

As educators, we play a crucial and active role as human detectors. We should not rely on the metrics used by AI detectors alone but combining them with our semantic and critical thinking abilities to discern between texts generated by humans and AI.

Criteria for Selecting An AI Detector

On top of that, it is also crucial if we select the right AI detector. Considerations of the following should be made when selecting an AI detector:  

• Track Record: Look for proven track record of identifying various types of plagiarism accurately.
• False Positive and False Negative Rates: Examine the rates of false positives (misidentifying human content as AI-generated) and false negatives (failing to detect AI-generated content). A balance between these rates is essential for reliable results. The combined result of false positive and false negative rates are reflected in the accuracy of the AI detector.
• Flexibility and Versatility: Check if the detector can handle different file formats and languages. 

Best Free AI Detectors for Teachers in 2024 Compared

Without further ado, let us dive into the finest AI detectors available for educators in 2024. We have meticulously handpicked the top 9 options that are highly recommended by educators themselves. 

Best for accuracy: Winston AI

Best for reports: AI Detector Pro and Winston AI

Best all-in-one tool: Scribbr

Comes with regular plagiarism detection: Turnitin, Scribbr and Winston AI

1. Winston AI (Our Educators’ Rating: ⭐️⭐️⭐️⭐️)

Winston AI is trusted by educators worldwide for this reason. Unlike many other free AI detectors, it did not incorrectly label any human text as AI-generated, and vice versa. It did well in mixed AI-and-human texts. 

🔎 How does it detect AI content? 

Winston AI uses a reverse engineering method which involves the use of NLP and machine learning to identify patterns of text that commonly occur in AI-generated texts. As such, it can identify content generated with ChatGPT, Bard, Bing Chat, Claude, and many more Large Language Models or AI chatbots. 

💙 Why do teachers like it?

The tool is quite accurate and is made for educators. It also comes with clear explanations, report and plagiarism detection features, as well as document upload feature. Additionally, it is quick and intuitive to use. Winston AI also uses OCR (Optical Character Recognition) technology which makes it super convenient for teachers who want to check hand-written submissions!

🧮 Accuracy: Claims to be 99.6% accurate! 

➕ False Positive Rate: Close to 0%.

➖ False Negative Rate: Fails to detect about 29% of AI-generated content according to this source. 

👎 Limitations?

• The free version is capped at 2000 words or credits.
• Need to create an account to use.
• Plagiarism detection feature is not available in the free version. 
• Absence of URL scanning.
• Only supports English and French languages at the moment.

2. CopyLeaks (Our Educators’ Rating: ⭐️⭐️⭐️)

CopyLeaks is one of the more well marketed AI detector out there, which promises an accuracy of 99.1% at detecting AI-generated content. The tool is not targeted for educators alone, but can also be used in other occasions by professionals in various industries from law to marketing. The platform is easy and intuitive to use, and you can use it online, though you will have to create a free account to increase the daily checks limit. Alternatively, you can also download CopyLeak’s free Google Chrome extension to check social media posts or webpages.

🔎 How does it detect AI content? 

CopyLeaks claims to use a “fight fire with fire” approach, using AI to detect AI-generated text. Similar to many other AI detectors, CopyLeaks can detect texts generated by GPT-3, GPT-3.5 and GPT-4 models, including ChatGPT. 

💙 Why do teachers like it?

CopyLeaks works super fast and can generate results in less than 1 minute, even for lengthy texts. The tool supports multiple languages and provides integration with your favourite API and LMS platforms. It also has a browser extension that can be seamlessly integrated into your browser to check any online pages. A further plus point is that it not only detects texts but also works well with uploaded files, URLs, and even texts within images.

🧮  Accuracy: Claims to be 99.1% accurate. 

➕ False Positive Rate: Claims to be 0.2%, but misidentifies 2/6 human-written content as AI-generated content from our test.

➖False Negative Rate: Fails to detect about 50% of AI-generated content according to this source. 

👎 Limitations?

• There is a limit on daily usage, which can be increased (not removed) by signing up for a free account. 
• Even though it provides an overall percentage indicating the likelihood that the text is AI-generated, it does not provide adequate explanations on the highlighted texts.
• Absence of plagiarism detection feature.

3. Content at Scale (Our Educators’ Rating: ⭐️⭐️⭐️)

Named as Product of the Day but Product Hunt for a reason, Content at Scale stands out as one of the best AI detectors around. The tool is quite accurate and fast in detecting AI-generated content. It combs through each sentence and can accurately tell you which is AI-generated and which is not. Even though it requires users to sign up for a free account, the effort is worth it given its reliability.

🔎 How does it detect AI content? 

Content at Scale has been trained on billions of pages of data across multiple Large Language Models (LLMs) and uses NLP to detect patterns, forecast probable word choices, and it also claims to understand sentence structure and other characteristics that lead to AI plagiarism. As such, it can effortlessly detect AI-generated text from GPT-3, GPT-3.5, GPT4, Claude and Bard.

💙 Why do teachers like it?

Apart from being accurate, Content at Scale also provides explanations on which part of the texts is likely AI-generated, which many of the free AI detectors lacks. It also supports multiple languages. No signup is required to use.

🧮 Accuracy: Claims to be 98.3% accurate. 

➕ False Positive Rate: Not publicized, misidentifies 2/6 human-written content as AI-generated content from our test.

➖False Negative Rate: Fails to detect about 29% of AI-generated content according to this source.

👎 Limitations?

• Not only an AI detector – it also provides solutions to create human-like AI content that bypass AI detectors. So teachers should be aware of the potential student misuse of these platforms to create unoriginal content. 
• Absence of URL scanning feature.
• Absence of file upload feature.
• Absence of plagiarism detection feature.

4. AI Detector Pro(Our Educators’ Rating: ⭐️⭐️⭐️⭐️)

AI Detector Pro is one of the many free AI detectors that actually provide a report indicating which part of the texts is likely AI-generated. It also provides users with 30 additional tools which include functions like text cleaner, word density counter, and many more for researchers, developers and content writers. 

🔎 How does it detect AI content? 

Like other AI detectors, AI Detector Pro is trained to find patterns in the data it is trained with. It can detect AI-generated content in GPT-2, GPT-3, GPT-4, GPT-J, and Bard. 

💙 Why do teachers like it?

On top of its detailed report clearly pinpointing which part of the text is generated by AI, AI Detector Pro has an additional feature called “AI Eraser” which allows users to amend the AI-generated content and replace them with alternative wordings based on the AI suggestions, and rescan the content accordingly. This is helpful if educators want to produce suggestions and feedback for student work with some additional help. AI Detector Pro also can content from website URLs, and it offers a money-back guarantee policy if you ever decide to go for the paid version.

🧮 Accuracy: Not publicized

➕ False Positive Rate: Not publicized, misidentifies 2/6 human-written content as AI-generated content from our test.

➖False Negative Rate: Detects all AI-generated content accurately from our test.

👎 Limitations?

• Currently only works for English language texts. 
• The free version is also only limited to 3 reports.
• Need to sign up for a free account to use.
• Absence of URL scanning feature.
• Absence of plagiarism detection feature.

5. Scibbr (Our Educators’ Rating: ⭐️⭐️)

Scribbr is powered by Turnitin, the famous plagiarism checker among educators. Scribbr not only detects plagiarism from web pages and publications, but also AI-generated texts. It also comes with it other handy features for teachers including spell checker, paraphraser, text summarizer, proofreading, college essay editing and coaching, and more. And the best part is, as compared to Turnitin, it offers teachers a free version.

🔎 How does it detect AI content? 

Similar to Turitin, it detects AI-generated content through the principle of perplexity, or the predictability of the words used. Since it is powered by Turnitin AI, it can detect content from the GPT-3, GPT-3.5 and GPT-4 language models, including ChatGPT. Scribbr will scan your text and return with a percentage of how likely the content is written by AI.

💙 Why do teachers like it?

Scibbr supports multiple languages including Spanish, French, German, and many more. It can also be used to edit citation for academic papers easily, to ensure academic integrity. Scribbr is more than just an AI detector; it is one of the rare tools that also offers features such as a plagiarism checker, citation generator, text summarizer, and proofreader. This all-encompassing tool can be seen as a valuable assistant for teachers seeking comprehensive support.

🧮 Accuracy: 98% accurate. 

➕ False Positive Rate: Misidentifies 2/6 human-written content as AI-generated content from our test.

False Negative Rate: Sadly, misidentifies almost all AI-generated content as written by human from our test.

👎 Limitations?

• Can only check up to 500 words at a time for the free version. 
• Does not provide detailed explanation of which part of the text is generated by AI.
• Absence of URL scanning feature.
• Does not work sometimes. 

6. Sapling (Our Educators’ Rating: ⭐️⭐️)

Developed by former researchers from Stanford, Google and University of California, Berkeley, Sapling is intuitive and straightforward to use and there is no sign up required to use the tool. Simply paste the text you want to check and you will be able to receive instant result. 

🔎 How does it detect AI content? 

Sapling uses a mixture of perplexity and burstiness to measure whether a piece of content is likely generated by AI. It can detect all texts generated by GPT-3, GPT-3.5 and GPT-4 models. As for how the tool works, it uses sentence detector and pre-sentence detector to judge the probability of AI-generated texts. 

💙 Why do teachers like it?

As compared to many free tools available in the market, Sapling sometimes does a rather good job in correctly highlighting AI-generated texts in mixed AI-and-human texts. There is also no need to sign up an account or pay a single cent to use the tool. Sapling is also available as a browser extension for convenience.

🧮 Accuracy: Not publicized.  

➕ False Positive Rate: Misidentifies 2/6 human-written content as AI-generated content from our test.

➖False Negative Rate: Varies. In our test, it falsely identifies almost all AI-generated content as human-written. But according to this source, it fails to detect only about 37.5% of AI-generated content.

👎 Limitations?

• Its accuracy is sometimes questionable. 
• It is not entirely clear what the highlighted texts mean as no explanations are given.  
• Absence of URL scanning feature.
• Absence of file upload feature.
• Absence of plagiarism detection feature.

7. GPTKit(Our Educators’ Rating: ⭐️⭐️⭐️)

Easy and intuitive to use without sign-in required, it is not difficult to see why it quickly gains popularity. GPTKit also uses multi-modal approach to detect AI-generated texts, hence boosting its reliability. 

🔎 How does it detect AI content? 

GPTKit claims to use 6 different AI-based content detection techniques, which include DistilBERT, GLTR, Perplexity, RoBERTa and RoBERTa (Based). We don’t need to know the technicalities, all we need to know is that we can expect a higher accuracy in its results compared to some of the other free AI detectors. It was also trained with over 1 million datasets which include ChatGPT-generated and human-generated texts from various sources from webpages and Reddit to news articles. 

💙 Why do teachers like it?

No sign-in is required to use the tool. It also provides quick report on the authenticity and reality of the content scanned which many free AI detectors lack.

🧮 Accuracy: Claims to be approximately 93% accurate.

➕ False Positive Rate: Misidentifies 2/3 human-written content as AI-generated content from our test.

➖False Negative Rate: Detects all AI-generated content, though with varying confidence.

👎 Limitations?

• Free version is limited to only 1-2 scans.
• Currently only works for English language texts. 
• Does not tell you which part of the text is AI-generated and which part is written by human. 
• Absence of URL scanning feature.
• Absence of plagiarism detection feature.

8. GPTZero (Our Educators’ Rating: ⭐️⭐️)

GPTZero is developed by OpenAI, the company behind ChatGPT. And because it is free to use and built for educators, ZeroGPT has become one of the favourite AI detectors of educators and teachers alike.

Note: GPTZero is a different tool compared to ZeroGPT, and the former has been tested to be a more accurate tool overall than the latter.

🔎 How does it detect AI content? 

GPTZero also uses the burstiness and perplexity metrics to detect AI-generated content. As such, it works well across a wide range of AI language models, including ChatGPT, LLaMA, and AI services based on those models.

💙 Why do teachers like it?

GPTZero is trained for student writing and ed-tech use cases, which means it can do a rather reliable job in detecting AI-generated content in student work. It is straightforward to use and does not require sign-in. The stats showing the perplexity and burstiness scores also help give educators a deeper insight into how likely a content is AI-generated. And perhaps the best part is that GPTZero offers API integration and allows bulk upload of different files.  

🧮 Accuracy: 98% as claimed by OpenAI

➕ False Positive Rate: Up to 20% according to this source. 

➖False Negative Rate: In our test, it is unable to confidently identify any of all 6 AI-generated content as human-written. 

👎 Limitations?

• GPTZero did warn educators that it cannot detect AI-generated text after it has been heavily modified after generation. 
• The data that is used to train GPTZero is also heavily biased towards English prose written by adults. So this may affect its accuracy in detecting texts in other languages or written by other demographics.
• The result uses phrases like “”Our ensemble of detectors have predicted different results for this text.”, and “Your texts may include parts written by AI.” which may not be too helpful for teachers without demonstrating clear confidence and providing clear explanations on the AI-generated segments.
• Free version is limited to only a few checks.
• Absence of URL scanning feature.
• Absence of plagiarism detection feature.

Turnitin (Our Educators’ Rating: ⭐️⭐️⭐️⭐️)

Now let’s talk about teachers’ all-time favourite plagiarism checker – Turnitin. The reason why we put Turnitin last is because it is a paid tool that comes with a rather long free trial. Turnitin has recently launched its own AI plagiarism checker feature with AI writing detection ability. Teachers can just upload their students’ submissions to Turnitin as usual, and the AI will be able to detect AI-generated content alongside plagiarised content.  

🔎 How does it detect AI content? 

Turnitin AI is trained to detect content from the GPT-3, GPT-3.5 and GPT-4 language models, including ChatGPT. It mainly detects AI-generated content through the principle of perplexity, or the predictability of the words used. Turnitin first breaks down a submission into segments and sentences and attribute each sentence to a score between 0 and 1, with 0 being a fully human-generated content and 1 being an AI-generated content. The scores are then average out to produce an overall prediction of how much text has been generated by AI.

💙 Why do teachers like it?

Apart from educators’ familiarity with Turnitin, Turnitin is also trained on data from other languages and subjects other than English including anthropology, geology, sociology, and others, so it can also be used to detect AI-plagiarised content in non-English language and subject pretty decently. It also seamlessly integrates with Learning Management System (LMS) like Blackboard which allows teachers to work from within a familiar environment.

🧮 Accuracy: Claims to be 98% accurate overall. 

➕ False Positive Rate: Less than 1%.

➖False Negative Rate: Not available.

👎 Limitations?

• Paid tool, with 60-day free trial for teachers. *Since it is a popular plagiarism checker among institutions, schools often have a subscription with Turnitin so be sure to check with your institution before subscribing. 
• Some teachers did mention that false positive rate can be quite different from what was advertised, and can go up to a whopping 62.5%, even for English submissions. 

Tips for Effective Plagiarism Prevention and Education 

Apart from utilising AI plagiarism tools, effective plagiarism prevention and education are essential to promote academic integrity and foster a culture of originality in educational institutions. Here are some valuable tips for achieving this:

• Clearly Define Plagiarism: It is important to provide a clear and comprehensive definition of plagiarism to students. Do not expect students to know this by common sense. Explain what constitutes plagiarism, including copying someone else’s work, improper paraphrasing, and not giving proper credit to the original source.
• Educate About Consequences: Educate students about the consequences of plagiarism and establish proper guidelines. Raise awareness on how plagiarism can damage their academic reputation, lead to disciplinary actions, and erode trust between students and educators.
• Teach Proper Citation and Referencing: Offer workshops and classes to teach students on proper citation and referencing styles (e.g., APA, MLA). And lead by example.
• Promote Academic Integrity Policies: Communicate and always remind students of the academic integrity policies across the institution. 
• Promote Critical Thinking: Finally, and perhaps most importantly, is to teach critical thinking and original analysis in students’ work, as well as promoting the benefits of practicing critical thinking, through problem-solving activities and fact-checking activities. This will foster the desire to produce authentic and original thoughts and work.
• Consider Assigning Unique Topics and Prompts: It helps to provide unique topics or prompts for assignments, reducing the likelihood of finding pre-existing content online.
  • Consider using ClassPoint’s AI quiz generator to create prompts and questions using advanced AI algorithms. This tool can provide you with creative and limitless variations on the same topic. Here’s how you can create an AI quiz in PowerPoint effortlessly.

• Consider Adjusting Exam Methods: Consider reintroducing traditional pen and paper for essay writing or test completion to reduce the use of AI-generated content.

By putting these tips into practice, educators can help students develop a strong sense of responsibility and authenticity. This will foster a supportive and future-ready community that embraces Classroom AI with strong academic integrity at its core.

Final Thoughts

We hope these 9 free AI plagiarism checkers, endorsed and recommended by educators can help give you peace of mind admist the rapid rise of AI-generated content in student work using chatbots and AI writing tools. With a detailed explanation on how AI plagiarism checkers work, as well as tips you can implement to prevent plagiarism, we hope they can help alleviate some of your concerns about the rise of this new breed of “undetectable” plagiarism.

Still, as educators, we shouldn’t blindly rely on the readily available AI technologies built to counter AI-generated content, it is important to infuse a layer of human-proof by integrating human judgment to maintain the authenticity and originality of student work. We wish you all the very best in navigating the evolving landscape of AI while upholding the principles of academic integrity!

For the latest tips, trends and tools about AI in education, read our A-Z guide to AI in education!

Further Readings