This article reviews 7 AI content detector tools. We tested and compared them using AI-generated, human-written, and human-edited texts (including attempts to bypass detection) and now we’re sharing the results.
And since AI is everywhere and was forced on us by basically every medium and blog out there (when my mother-in-law asked me “How do you use AI?” I know we are at a pretty high adoption rate), some businesses are now scrutinized over using AI-generated content for fear of backlash or legal issues.
As AI-generated text becomes harder to distinguish from human writing, how can you reliably tell the difference? We wrote this guide for marketers, publishers, and content teams who actually rely on AI detection results and not just casual checks. Let’s go.
TL;DR: Best AI content detectors
- No AI detector is 100% accurate. All tools produced false positives or false negatives in at least some scenarios.
- GPTZero and QuillBot delivered the most consistent accuracy across AI-generated, human-written, and human-edited AI texts.
- Human-edited AI content remains the hardest to detect, even for leading tools.
- Free plans vary wildly: some are genuinely usable, others are too limited to evaluate properly.
- AI detection should be used as a spot-check, not as definitive proof of authorship.
- All tools in this article were tested manually using the same set of AI-generated, human-written, and human-edited texts to ensure consistent comparison.
- This article was originally published in 2024. Core testing and results were finished in 2025. It was editorially updated in 2026 to improve clarity, structure, and contextual accuracy as AI detection tools continue to evolve.
What is an AI text detector?
AI text detectors are tools meant to identify content written by artificial intelligence. As AI writing gets better, and some prompt wizards are able to generate output practically indistinguishable from human writing, the best AI content detectors still promise to help.
These tools are definitely on the rise. According to WiseGuy’s Global AI Content Detector Market Research Report, the estimated AI content detectors market is expected to grow from $2,310 Billion in 2025 to $15 Billion by 2035. These days everyone is expected to be more and more productive. Subsequently, the use of AI tools is increasing to match those expectations. And then suddenly various entities require people who just got comfortable with this new tech to stop the use of AI altogether for different reasons, could it be a growing pool of factual mistakes, questions about AI ethics, or just a belief that 100% of content generated with the help of AI is bad. So it’s not surprising to see these numbers.
Most AI content detectors have a simple interface: paste your text, click a button, and get the verdict: AI or not AI. Some provide detailed breakdowns of which sections of the text impacted the judgment results the most. Some tools will offer API access and support multiple languages.
Each of the AI text detector tools has its own way of identifying AI. It’s not some kind of quiz asking if you are a robot, but rather algorithms and rules analyzing writing patterns, grammar, choices of words, and the way the sentences are written. The combined results allow the tools to make an educated guess about whether or not the text was written by a machine. But let’s get to the nitty gritty: the basics of AI detection algorithms.
How exactly does an AI detection tool work?
In a nutshell, AI detectors are looking for specific patterns and characteristics in a text and those often can help differentiate AI content from human-written text. Every tool has its own unique proprietary blend of technologies to look at, but there are some common concepts used for AI detection.
One of them is perplexity. It measures the unpredictability of the text. AI-generated content usually has lower perplexity, meaning that it’s easier to predict which word comes next. Human writing tends to be more perplexing, include more curious word choices, and feature occasional typos (sure, it’s not something to be proud of under normal circumstances, but in the age of AI, surprisingly it is).
Another concept these tools use is burstiness, and it’s related to variation in sentence length and structure. AI text usually has lower burstiness, with all sentences being of similar length. Human writing usually shows higher burstiness and sometimes comes with excessive love for passive voice and weirdly long sentences.
Based on analysis of these and other factors, most AI detection tools provide a probability score of whether the text is human or machine-generated. But as mentioned before, all AI detectors are different and as AI writing gets better (and users learn how to use it more efficiently), AI detection developers should always make adjustments to keep up. Ultimately it means that no tool is 100% foolproof on how to detect AI writing.
7 best AI detectors
But is there a tool that is clearly superior to others? Or are all pretty much equal? I decided to put it to the test. Let’s dive into our findings and see how the AI detection tools performed against each other in real-world scenarios.
How did we choose and evaluate the tools?
The tool selection process included cross-referencing multiple “best AI detector” rankings on Google. I chose tools that appeared more often across these lists. I also included a few tools that were not on those lists but showed up on top of Google search results for the query “best AI tool.”
The main focus of this comparison is accuracy, but pricing and functionality have been also considered. All tools were tested using their free versions. (Some tools were not generous enough with their free plans, so I had to be creative with new accounts and clearing cache and cookies).
To really put these detectors to the test, I fed them different types of AI-generated, human-edited, and human texts. I started with simple ChatGPT and Claude outputs, then progressed to more complex prompts including rewriting texts to bypass detection, outputs mimicking well-known human content creators, and prompt training on distinctive human writing styles. I also tested human-edited AI outputs (it was a substantial amount of effort, about 50% of the initial text was edited) and fully human-written content.
You can see all the text samples in the slideshow below:
For those who came to know what the results are, here’s a detailed breakdown of the tools’ performance at the time of testing, where the % in the table is the share of human writing predicted by each tool.
| Task | Winston Al | Originaliy.Al | GPTZero | ZeroGPT | Smodin | Hive | QuillBot |
| Basic prompt ChatGPT | 0% | 0% | 0% | 100% | 0% | 0.01% | 0% |
| Basic prompt Claude | 0% | 0% | 0% | 19% | 0% | 0.01% | 0% |
| Rewrite to bypass Al detection ChatGPT | 0% | 1% | 0% | 70% | 0% | 100% | 0% |
| Rewrite to bypass Al detection Claude | 0% | 100% | 0% | 53% | 0% | 0.01% | 0% |
| Rewrite in the style of a well-known human ChatGPT | 0% | 36% | 0% | 100% | 0% | 100% | 0% |
| Rewrite in the style of a well-known human Claude | 0% | 95% | 24% | 84% | 24% | 99.3% | 0% |
| Write based on samples of very distinct writing of an actual human ChatGPT | 0% | 0% | 0% | 0% | 0% | 100% | 0% |
| Write based on samples of very distinct writing of an actual human Claude | 0% | 100% | 12% | 84% | 0% | 100% | 0% |
| Output written to bypass Al detection with human edits ChatGPT | 6% | 97% | 5% | 85% | 100% | 100% | 37% |
| Output written to bypass Al detection with human edits Claude | 4% | 100% | 81% | 100% | 100% | 89.9% | 100% |
| Human Text | 100% | 100% | 96% | 100% | 100% | 100% | 100% |
Across all tools we tested, false positives and false negatives remained a consistent issue. In particular, human-edited AI content proved difficult for most detectors to classify reliably, reinforcing that AI detection results should be treated as probabilistic signals rather than definitive judgments.
And if you want to learn about each tool in greater detail, please, read the full report below.
Winston AI
Winston AI is a full-scope AI content detection tool that offers lots of amazing features: AI text and image detection, plagiarism checker, and even handwriting analysis. It stands out for its user-friendly interface and generous free tier. And, as it turned out, pretty good accuracy.
How AI detection works in this tool:
Winston AI uses a combination of data training, linguistic analysis, and algorithms for pattern recognition. It looks at things like perplexity and burstiness to determine if content is likely to be produced by AI. It gives a “Human Score” showing the probability of human authorship and features an AI prediction map indicating sections of the texts that were potentially generated by AI.
Pricing:
Winston AI offers a free tier with 2,000 credits (1 credit per word) and a 14-day trial of premium features. Paid plans applicable for teams start at $29/month (or $19/month if paid annually). This tier includes 200,000 credits/month and features like more sophisticated plagiarism detection and shareable PDF reports.
Accuracy test results:
Winston AI performed well in identifying both AI and human-written content. However, it showed some inconsistencies:
- It accurately detected AI-generated text, even when heavily edited, giving low human scores (6% for ChatGPT and 4% for Claude).
- There were some discrepancies in text with human edits. For instance, while the overall score was 4% human, the detailed analysis said the whole text was likely human-generated.
- The tool was overly strict in classifying heavily edited AI text as AI, potentially leading to false negatives.
Accuracy verdict
Overall, Winston AI seems to be a great tool with decent accuracy, but users should be aware of potential inconsistencies in reporting, especially when dealing with human-edited content.
It’s strong at detecting raw AI content, but overly strict with heavily edited AI text and occasionally inconsistent in reporting.
Originality.AI
Originality.AI is another AI content detection tool for serious publishers that claims to hit a 99% accuracy rate. It offers AI detection, plagiarism checking, and readability analysis catering to teams that manage large volumes of content.
How AI detection works in this tool:
Originality.AI doesn’t exactly explain how their detection works, but they claim to identify texts generated by ChatGPT, GPT-4, Claude, Llama, and Gemini. They also mention that one of the reasons why their tool outperforms other AI detection tools is that the “AI algorithms at Originality.AI use natural language processing techniques that require a lot more compute power.” The same being the reason why their “free” tier is so stingy.
Pricing:
The tool is not very free-user friendly, offering only 3 free checks through the web app upon registration with blurred detailed results. The cheapest team-suitable plan starts at $19.95/month (or $14.95/month if paid annually) providing 1,000 credits per month (1 credit = 100 words scanned).
Accuracy test results:
Originality.AI’s performance was mixed in our tests:
- It claims high accuracy (98-99%+) and low false positive rates across its different models.
- However, in some cases, it identified fully AI-written text (including text rewritten to bypass AI detection and AI writing based on distinct human samples) as 100% human.
- The blurred results in the free version made it difficult to fully assess and justify some of its incorrect identifications.
Accuracy verdict
While Originality.AI offers tons of bells and whistles for content management and claims high accuracy, the tests revealed some serious flaws in its AI detection capabilities and accuracy.
It claims very high accuracy, but struggled with advanced AI rewriting and human-style prompts in our tests.
GPTZero
GPTZero is a leading AI content detection tool that stands out for its generous free plan and comprehensive features. It’s designed to work for both individual users and teams, offering a range of AI detection capabilities including pretty robust analytics.
How AI detection works in this tool:
According to the tool’s documentation, GPTZero uses two key components in its detection process: perplexity measurement and burstiness analysis (and we talked about both in the intro part of this report). The tool compares these metrics against benchmarks for human and AI-written text to make its determination. Very straightforward.
Pricing:
GPTZero offers a substantial free plan with up to 10,000 words per month and basic team collaboration features. Paid plans start at $10/month (billed annually) or $15/month, offering increased word limits and advanced features like plagiarism scanning. Team plans with multiple seats start at $24/month per seat.
Accuracy test results:
GPTZero demonstrated strong performance in our tests:
- It accurately identified AI-generated content in most cases.
- The tool showed high sensitivity, sometimes detecting AI influence even in heavily human-edited texts.
- There were occasional false positives in fully human-written texts, but these were minimal.
- GPTZero tended to be conservative in its “human” scoring, often giving lower human percentages even for significantly human-edited AI text.
Accuracy verdict
Overall, GPTZero proves to be the best in accuracy, though it may err on the side of caution when assessing human writing. Its accuracy and generous free tier make it a strong player in the AI detection tool market.
It’s the most reliable overall performer, though sometimes conservative and prone to false positives on human-edited content.
ZeroGPT
ZeroGPT is one of the OG of AI detection tools. Especially given that most of us can be more than happy with its free tier. It also offers a range of features beyond just AI detection including summarization, paraphrasing, and translation. It stands out for its free version and pay-as-you-go API option for businesses.
How AI detection works in this tool:
ZeroGPT uses what they call DeepAnalyse™ Technology, a multi-stage methodology that analyzes text from macro to micro levels. The tool implements deep learning based on extensive text collections including internet content, educational datasets, and proprietary synthetic AI datasets.
Pricing:
ZeroGPT offers a generous free plan with 15,000 characters per AI detection. The Pro version, priced at $7.99/month (billed annually) or $9.99/month (billed monthly), increases this limit to 100,000 characters. For businesses, there’s a pay-as-you-go API option starting at $0.034 per 1,000 words.
Accuracy test results:
Despite its sophisticated technology claims, ZeroGPT showed inconsistent performance in our tests:
- It incorrectly identified output from a basic ChatGPT prompt as 100% human.
- It also classified text rewritten by ChatGPT in the style of a well-known human as 100% human.
- The tool only correctly identified as AI (100%) the text based on samples of very distinct human writing from ChatGPT.
- Interestingly, the same type of text from Claude was classified as 84% human.
Accuracy verdict
Out of all the services on our best AI content detectors list, ZeroGPT has the most substantial free tier. However, our testing showed that its AI detection can be questionable.
In short, it has a generous free tier, but inconsistent results, especially with AI content rewritten in human styles.
Smodin
Smodin is another popular AI content detection tool that comes with additional features like grammar checking and text improvement suggestions. It has a pretty goofy and outdated interface that still should work for a wide range of users, from students and educators to people writing for a living and businesses.
How AI detection works in this tool:
According to Smodin’s documentation, the tool uses advanced algorithms to analyze text for AI interventions. The tool examines factors such as language consistency, writing complexity, and factual errors to decide if any AI was involved in content creation. It claims to detect text generated by various AI models including ChatGPT, Gemini, and Azure.
Pricing:
Smodin offers a free plan with limited features (5,000 characters per text, 5 uses per week). The Essentials plan, priced at $12/month (annual billing) or $15/month (monthly billing), provides more advanced features like API access, higher character limits (15,000 per text), and unlimited daily uses.
Accuracy test results:
Smodin showed mixed results in our accuracy tests:
- The tool identified fully AI-generated texts quite accurately.
- However, it was overly generous in labeling texts with any human involvement. For instance, it said that human-edited AI texts were 100% human-written, where a more nuanced classification (e.g., 80% human) could have been more accurate.
- The free plan’s limitations (5 texts per week) make it hard to thoroughly evaluate the tool’s effectiveness before committing to a paid plan.
Accuracy verdict
While Smodin offers promising features and claims high accuracy rates (91% for AI documents, 99% for human documents), according to the test results, it may struggle with nuanced cases involving partial AI involvement. Also, the fact that the free tier is so limited can scare off potential users.
So, it’s accurate for fully AI-generated text, but too forgiving when even minimal human edits are involved.
Hive
Hive is an AI content detection tool that offers both text and image analysis capabilities. It claims to use advanced machine learning algorithms for accurate detection and classification of AI-generated content.
How AI detection works in this tool:
Hive uses a multi-step process for content analysis. For text, it uses feature extraction and pre-trained models to identify AI-generated content. The tool claims to perform both binary classification (AI vs. human) and source classification (identifying specific AI generators), providing confidence scores for each classification.
Pricing:
Hive’s pricing structure lacks transparency. You must personally contact the sales department to learn about your potential costs and no pricing data is publicly available, at the moment of working on this research. With a minimum of 750 characters and a maximum of 8,192 characters per try, the free tier only provides 2 text analyses.
Accuracy test results:
Our tests found serious flaws in Hive’s performance:
- The tool’s accuracy was pretty low, often identifying 100% AI samples as human-written.
- The limited free tier makes it difficult to understand whether or not the tool is working before committing to a paid plan. And the lack of pricing transparency complicates the decision-making process even more.
Accuracy verdict
While Hive’s website looks very sleek and presents what’s going on under the tool’s hood no less than sophisticated, the tests’ results suggest its actual performance is a bit less than you would expect. Poor accuracy, limited free tier, and unclear pricing make it difficult to recommend this tool.
It underperformed across multiple scenarios, with frequent misclassification of AI content as human-written.
QuillBot AI Detector
QuillBot AI Detector is a user-friendly tool designed to identify AI-generated content including text refined by paraphrasing tools or grammar checkers. It stands out for its VERY generous free plan and detailed analysis capabilities and also offers writing tools.
How AI detection works in this tool:
QuillBot’s AI detector uses advanced algorithms to analyze text for indicators of AI generation, such as repeated words, awkward phrasing, and unnatural flow. The tool provides a detailed report highlighting specific sections of text that appear to be AI-generated.
Pricing:
QuillBot offers a generous free plan, allowing users to scan unlimited texts of up to 1,200 words each at no cost. Premium is available, though it doesn’t seem to increase the word limit for AI detection. Team plans start at $3.75 a month per seat for 5-10 seats (billed annually).
Accuracy test results:
QuillBot AI Detector demonstrated impressive performance in our tests:
- The tool had a high accuracy across different scenarios, performing on par with top-rated detection tools in this sample set.
- The detection accuracy was pretty high and consistent across different types of content.
- The detector was able to identify nuances in partially AI-generated or human-edited AI content. Even though it wasn’t 100% correct, it offered more accurate grading than other competitors.
Accuracy verdict
I love QuillBot AI Detector for its generous free tier and very decent accuracy. The unlimited free scans make it an excellent option for those looking for frequent AI content checks without robbing the bank.
It shows consistently strong performance across test cases, with one of the best free plans available.
Honorable mention: Monica AI Detector
Monica AI Detector claims that it can identify content generated by 8 cutting-edge AI models such as GPT-4 with 98% accuracy, and simultaneously provide a “humanized” text rewriting function. It is suitable for individual users for a variety of purposes.
How AI detection works in this tool:
Monica explains on its page that it combines the advantages of AI content detection tools such as ZeroGPT, GPTZero and Copyleaks, integrating multiple top AI detectors into one, providing excellent detection accuracy. At the same time, it also analyzes through real-time API calls to ensure that the detection and rewriting results are based on real and latest data.
Pricing:
Monica’s free plan allows users to detect texts of less than 250 words each time and provides ZeroGPT’s detection results. The PRO plan ($8.3/month) increases the detection limit to 10,000 words, while unlocking GPTZero and Copyleaks’ detection results and other AI tools on the platform. The Unlimited plan ($12.4/month) provides unlimited use of all features.
Accuracy test results:
Monica AI Detector can accurately identify AI- and human-written content:
- Even after the text has been edited many times, it can still correctly determine that it is generated by AI.
- We can see that higher accuracy is achieved due to the presence of multiple models supporting the detection results.
- Monica was unable to respond to multiple languages immediately, and its accuracy was also worrying.
Accuracy verdict
In general, Monica combines three widely recognized and effective detection models, which enables it to provide accurate judgments when testing more complex texts. Therefore, it is a trustworthy tool.
It has high accuracy thanks to multi-model detection, but language support and response reliability can be inconsistent.
Why some popular AI detectors didn’t make our main list
There are several other AI content detectors that frequently appear in “best AI detector” reviews and recommendations. While these tools are quite popular, we didn’t include them in our main comparison because they either overlapped with other tools or required a different evaluation methodology.
Sapling
Sapling is praised for its AI detection accuracy and is often featured in editorial roundups. However, at the time of our testing, Sapling’s detector overlapped heavily in approach and output with tools already included in the list, which didn’t offer enough extra insight for comparative testing. So, we chose to focus on tools with more distinct detection behavior.
Copyleaks
Copyleaks is also a strong solution for plagiarism detection and document scanning, and it’s a fact that it’s especially popular in educational and enterprise circles. However, its AI detection features are very much connected to its plagiarism workflows and credit-based scanning, which made it less suitable for the standalone detection scenarios we tested in this article.
Pangram Labs
Pangram Labs positions itself as an enterprise-grade AI detection platform and is mostly used by academic institutions and publishers. It offers advanced features, access limitations and a focus on institutional workflows, but it all also meant that it didn’t align well with our goal of testing tools under typical free or entry-level usage conditions.
Detecting-AI
Detecting-AI combines AI detection with humanization, rewriting, and other content tools. Its multu-purpusefullness can blur the line between detection and generation, though, so we excluded it from the main list to keep the comparison focused strictly on detection accuracy.
These tools may still be a good fit depending on a use case, but excluding them let us keep the comparison more focused, consistent, and directly comparable across all scenarios.
Final comparison table
| Best for | Tool |
| Best overall accuracy | GPTZero |
| Best free AI detector | QuillBot AI Detector |
| Best for educators and institutions | Winston AI |
| Best for publishers and teams | Originality.AI |
| Best for quick spot checks | ZeroGPT |
| Best for AI + writing tools combo | QuillBot |
| Least reliable in our tests | Hive |
Final thoughts
While the world of AI detection tools is quite mysterious and complex, I hope that readers of Selzy blog can benefit from the findings in this report. To wrap it up, GPTZero and QuillBot offer the best value in regards to accuracy and price. Use these tools to spot-check your email content, if you’re experimenting with AI writing assistants, to make sure your messages still sound authentic.
AI in email marketing is popular and widespread. Still, the most effective emails probably come from a deep understanding of your audience — and that is likely a skill only accessible to humans. (Although it’s another data point we should test in one of the future articles).
All in all, no detector is perfect and even the best tools throw false positives every once in a while, so, don’t let all AI paranoia stay in the way of your creativity. Always focus on value-driven content that is helpful to your audience, AI or not.
FAQ: AI content detectors
What is an AI content detector?
An AI content detector is a tool that estimates whether a piece of text was written by a human or generated by artificial intelligence. It analyzes patterns such as predictability, sentence structure, and word choice to produce a probability score, not a definitive verdict.
Are AI content detectors accurate?
AI content detectors are not 100% accurate. In practice, all tools can produce false positives or false negatives, especially when AI-generated text has been edited by a human.
Can AI content detectors detect human-edited AI text?
Human-edited AI content is the hardest case for detection. Once AI output is significantly rewritten, most detectors struggle to classify it reliably, which limits their usefulness as proof of authorship.
Is there a best AI content detector?
There is no single best AI content detector for every use case. Some tools are better at detecting raw AI text, while others are more conservative and may flag human writing. The right choice depends on accuracy needs, usage limits, and reporting features.
Should AI content detectors be trusted as definitive proof?
No. AI content detectors should be used as supporting tools, not as final proof. Their results are best treated as indicators that require human judgment and contextual review.
New and noteworthy on our blog 
