As AI-generated content becomes more common, the need to verify whether text was written by a human or a machine is growing fast, especially in education, online publishing, and business.
That’s where AI writing detectors come in!
These AI-powered tools are designed to analyze and evaluate written content to help you accurately identify AI-generated content.
In this in-depth review of the top AI writing detection tools, we break down what they are, how they work, the factors that influence their accuracy, and how accurate they really are.
We tested each tool hands-on using the same content samples to give you a clear, side-by-side comparison of their performance.
If you’re looking for reliable, human-user insights on which AI detectors deliver the best results, we’ve got you covered!
An AI writing detection tool is a software application that analyzes written text to determine the likelihood that it was generated by an AI model rather than a human.
These tools are trained on large datasets of human- and AI-written content to identify patterns such as word predictability, sentence structure, and stylistic features.
By comparing these patterns, the tool assigns a probability or confidence score indicating whether or not the content is AI-generated.
Common use cases for AI writing detectors include:
In all of these use cases, AI detectors help verify the authorship and originality of written content by flagging cases where additional assessment may be required to meet the required standards.
In simple terms, AI content detection tools analyze patterns in written text to assess the likelihood of it being generated by an AI model rather than written by a human.
AI copywriting tools generate content by predicting the next word in a sentence based on patterns learned from the datasets they were trained on.
As a result, AI-generated text often shows statistical regularities, such as high fluency, low variance in sentence structure, and predictable phrasing.
Large language models (LLMs), like ChatGPT, are trained on massive datasets, allowing them to base their predictions with a high level of accuracy.
However, they’re still fairly predictable because the sentence structure (sequence of words used) is based on a pattern that is, well, predictable.
Most AI writing detector tools are AI models themselves, trained using machine learning algorithms, similar in architecture to the language models they aim to detect.
They’re trained on large datasets of both human-written and AI-generated text to recognize the statistical and stylistic patterns that distinguish the two.
For example, they might detect differences in sentence variety, word predictability, or how concepts are developed throughout a passage.
Some detectors use classifiers (like logistic regression or neural networks), while others rely on perplexity scores, which are a measure of how “surprised” a model is by a given sequence of words. Lower perplexity scores usually indicate that the text is AI-generated.
Recent studies show that some leading AI-writing detection tools can achieve over 90% accuracy.
However, an academic review of 14 detectors published in the International Journal for Educational Integrity in 2023 found that less than half achieved more than 70% accuracy overall.
The level of accuracy reported varied most between unedited, fully AI-generated text and content that was paraphrased or edited by humans.
Some tools also show high false-positive rates, particularly for non-native English writers.
While AI detectors are incredibly valuable for anyone who needs help verifying the originality and authenticity of a written text, they’re not foolproof.
The accuracy of AI detection tools depends on numerous factors relating to both the characteristics of the text and the capabilities of the tool itself.
With so many variables, it’s almost impossible for any detector to be completely accurate for every use case, in every context.
That said, like all AI algorithms, they will continually improve as the datasets they’re processing expand with use and additional training.
To find the best AI writing detectors available, we looked at dozens of the tools available, existing software reviews, and did some Reddit deep dives to get perspectives from actual users.
From there, we chose the tools that looked the most promising and set about testing them to see how accurate they were.
We tested them using variations of a 1500 word text:
We wanted to provide a simple, apples-to-apples comparison, so we used the same writing samples to test each tool.
As we’re in the marketing niche, we used marketing-related samples, which, of course, limits our testing and test results to those applicable to this type of content.
Accuracy results could be very different for content in more specialized things like legal, technical, or academic writing.
We recommend that you run some of your own tests if you’re looking for a more specialized tool (like Turnitin, which is specifically for educational institutions).
Here are our detailed reviews of the tools we tested, including the test results and our observations and experience using them, as well as their key features and pricing:
Originality AI is a robust solution designed for publishers, marketers, and content creators. It combines AI-generated content detection, plagiarism checking, readability scoring, and fact-checking within one platform.
It offers AI writing detection for content from recent models like GPT‑4, Claude, and Gemini, for both fully AI‑generated and paraphrased text, such as content processed through text spinners and paraphrasing tools.
Originality AI also offers team management features, API access, a Chrome extension, and a useful website scanning tool to audit published web content for AI-generated content and plagiarism.
The free AI detector has a 750-word limit (you can buy additional credits once off or get a paid subscription), so we just used the first 750 words of each of our three samples for this test.
It was easy to use – just paste the text in and hit ‘scan’, and it gives you a % score, and highlights the text provided in different colours, showing the sections they’re most confident in are AI-generated.
The test results were pretty accurate:
Originality AI’s score of 93% confidence that the edited AI-generated text was written by AI shows that it wasn’t fooled by our editing, and it did pick up that the text was not fully AI-generated.
Here is what the test result looked like, with the color-coded highlights showing its assessment of different sections of the text:
Overall, Originality AI was easy to use and highly accurate, although the free tool was limited to 750 words at a time, which is a downside for anyone who only wants to use the AI detector and not the full suite of Originality AI’s features.
Website: https://originality.ai/
Surfer SEO is an AI-powered content optimization platform designed to help marketers, content creators, and SEO professionals write high-ranking articles based on real-time search data.
It analyzes top-performing pages for a given keyword and provides on-page SEO recommendations—such as word count, keyword usage, structure, and headings—to improve content visibility.
Surfer SEO is ideal for businesses, agencies, and individuals who want to streamline their SEO workflows, create data-driven content, and improve organic search performance.
In addition to Surfer SEO’s many content creation and optimization features, it offers an easy-to-use free AI detector!
Surfer SEO’s free AI detector is super easy to use – you just paste the text in and it gives you the percentage likely written by AI and the percentage likely written by a human in seconds.
And it was highly accurate:
Overall, it was super simple to use, it took the 1500-word text with no problem, it was really quick, and it was very accurate!
P2P Score: 4.8/5
Website: https://surferseo.com/ai-content-detector/
Grammarly, a well-known writing assistant tool, combines advanced grammar and spell checking with AI-driven style suggestions, plagiarism detection, readability insights, and now AI‑text detection.
Grammarly’s free AI detector analyzes your document and gives you a percentage score of the AI content identified.
If you download Grammarly and subscribe, it will break the analysis into sections when scoring the proportion likely generated by AI, underlining flagged passages, and providing more details.
It also integrates with Grammarly Authorship, which tracks how much text is typed, pasted, AI‑generated, or edited within the tool, offering a transparent report on authorship.
While its AI detection aims to support responsible writing, Grammarly acknowledges it is probabilistic and not definitive, often encouraging users to review flagged content thoughtfully.
Grammarly’s free AI detector was easy to use by simply pasting in the text and clicking the button.
However, it had a 10 0000 character limit, so we had to delete some of the content in the fully AI-generated sample, and it took a bit longer to do the analysis than some of the other tools.
The results were mixed:
Grammarly accurately identified the human-written sample as having 0% AI-generated text, and picked up 54% AI-generated text for the sample we’d edited, which is more or less in line with what the other tools we tested, but it only found 63% for the fully AI-generated, unedited sample.
Overall, Grammarly was easy to use (and free), but it wasn’t quite as accurate as some of the other tools we tested.
Website: https://www.grammarly.com/ai-detector
Founded in 2015, Copyleaks was developed with the aim of safeguarding intellectual property, upholding academic integrity, and governing responsible AI adoption.
Copyleaks is widely recognized as one of the most accurate detectors available and provides advanced detection of AI-generated and plagiarized text across 30+ languages.
It detects content from major LLMs, including ChatGPT, Gemini, and Claude, and flags paraphrased or plagiarized material.
The platform also offers API and LMS integrations, Google Docs and Chrome extensions, and features like AI Source Match and AI Phrases that highlight why specific content was flagged.
Copyleaks is a comprehensive tool, and after logging in, you have a dashboard with numerous options, from pasting text to uploading files or entering a URL.
Interestingly, it offers three levels of sensitivity for AI detection: text pasted straight from an LLM like ChatGPT, text that has been lightly edited, and text that has been heavily edited.
We chose level 3, the most ‘sensitive’ level, for our tests.
The test results were very accurate:
Overall, Copyleaks is a nice tool to use, and it is clearly designed for users who need in-depth analysis and detailed information on the results they get.
The scanner is also a text editor, so you can edit and re-scan as you go, and you can scan for plagiarism at the same time.
Copyleaks also offers really useful features like sharing and exporting the analysis report from within the platform.
It looks like a really solid choice for publishers, educational institutions, and anyone else who is handling a large volume of content and needs a comprehensive solution.
Website: https://copyleaks.com/
ZeroGPT is a free, web-based AI detector that analyzes submitted text to determine whether it was written by a human or generated by an AI model like ChatGPT, GPT‑4, Claude, or Gemini.
It uses advanced natural language processing techniques and machine learning algorithms trained on large datasets of both human-written and AI-generated content.
After submitting your text, ZeroGPT provides the percentage of AI-generated vs human-written text and highlights the detected origin at the sentence level, so you can see exactly which parts of the text it is basing its analysis on rather than just a general overall score.
ZeroGPT offers several additional tools, including a paraphraser, summarizer, plagiarism checker, and grammar/spell checker.
ZeroGPT was very easy to use by simply pasting your text into the box and clicking the ‘detect text‘ button.
It did its analysis quickly, highlighted the sentences it flagged as AI content, and provided a percentage score indicating how much of the text was identified as being AI-generated.
The results were pretty accurate:
It accurately identified the fully AI-generated, unedited text as AI/GPT writing and, clearly, the edited version of the AI-generated text wasn’t fooling ZeroGPT either!
It did pick up a false-positive of ‘27% AI-generated text’ in the fully human-written sample, but the highlighted sentences made it easy to check the sections it was flagging.
Website: https://www.zerogpt.com/
After testing the top-rated tools, we can confidently say that no AI writing detector is perfect, but we were impressed with the results they achieved.
Accuracy is affected by so many factors that it’s almost impossible for any tool to be 100% accurate, 100% of the time.
That said, they’re still incredibly useful for identifying content that is likely AI-generated!
Understanding how they work will help you choose the right solution for your needs and inform how you use it as part of your broader content review process.
Look for signs like repetitive phrasing, overly formal tone, predictable structure, and lack of personal insight. You can use AI detection tools to analyze text patterns and linguistic markers typical of large language models to get a good idea of the likelihood that a text was written using AI. Read the full review to learn more about how to identify AI-generated content and the best tools to use. You can reduce detectability by rewriting the content manually, adding personal experiences, varying sentence structure, and using natural language. Some use AI "humanizers," but results vary, and detection tools may still flag edited content. Read the full review to learn more about how ChatGPT content is detected and what makes it harder to identify, as well as the best tools used to detect text generated by ChatGPT and other AI language models. Top tools includeOriginality.AI, Copyleaks, Surfer SEO, Grammarly, and ZeroGPT. Each uses machine learning to identify linguistic patterns, with varying levels of accuracy and false-positive rates. Read the full review to learn more about the best AI writing detectors, how they work, and how accurate they are based on the tests we performed for this review. AI writing detectors analyze patterns like word predictability, sentence complexity, and structure. They compare text features against large datasets of human- and AI-generated writing to estimate the likelihood of AI authorship. Read the full review to learn more about how AI-generated content is detected and the best AI writing detectors to help you identify AI content.
How can you identify AI-generated content?
How can you make ChatGPT content undetectable?
What are the best AI content detection tools?
How is AI content detected?
Digital Marketing Institute: 10 Eye Opening AI Marketing Stats in 2025
Geeks for Geeks: Machine Learning Algorithms
IBM: What Are Large Language Models (LLMs)?
SurferSEO: 4 Ways AI Content Detectors Work to Spot AI
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