Which AI Detector is Accurate? [I tested 9]

AI detectors enable you to learn if the content is AI-generated or not.

In the era of Gen AI, it’s common for publications to receive low-effort and hard-to-distinguish AI-generated content. It lacks originality and can impact your SEO rankings. However, this should not be confused with plagiarism checkers, whose purpose is to find duplicate content on the internet.

Almost everyone uses AI in their day-to-day tasks. In fact, 73% of marketers report that they use AI to generate AI content, as per Botco.ai’s marketing report.

That’s why, in this post, I have listed 9 AI detectors that you can use to see if the content is AI-generated or not. I have personal experience using AI detectors, as it is a common practice to use AI detectors, especially in freelancing work.

Warning: These AI detectors are not 100% accurate. They only guide you in finding AI-generated content. That’s why it is always best to use your judgment before pointing fingers at your content creators. The false info can easily ruin your business relationship with writers.

To understand each tool’s effectiveness, I used various testing texts. These include:

• Human-written texts from scratch [For this, I’ll use my recent Landbot review content]
• GPT-4-turbo generated text
• GTP-4.5 generated text

Each of these texts is 1000-1500 words long. This is done to ensure fair comparison and remove AI detectors’ high sensitivity to smaller texts.

The accuracy metric is set to reflect how accurate the results are. To keep it simple to understand and what to expect, I have created the following:

• 80-90% confidence → Accuracy is determined to be high
• 75-80% confidence → Accuracy is determined to be medium
• 75% or lower → Accuracy is determined to be low.

To help you choose the right platform, I have tested the following AI detectors based on their accuracy, API support, and pricing.

• 1. ZeroGPT
• 2. Originality.ai
• 3. QuillBot
• 4. GPTZero
• 5. Grammarly AI Detector
• 6. Scribbr
• 7. CopyLeaks
• 8. Undetectable
• 9. Writer.com AI Detector
• Show moreShow less

AI Detector Comparison

Tool	Accuracy [Based on Geekflare tests]	Free to use	API Support	Price per month
ZeroGPT	High	Yes [up to 15000 characters]	Yes	$7.99
Originality AI Checker	High	No	Yes	$12.95
Quillbot	High	Yes [up to 1200 words]	No	$4.17
GPTZero	High	Yes [up to 5000 characters]	Yes	$8.33
Grammarly AI Detector	High	Yes [up to 10000 characters]	Yes	$12
Scribbr AI Detector	High	Yes [up to 1200 words]	No	$4.17
Copyleaks	High	Yes	Yes	$13.99
Undetectable	High	Yes	Yes	$5
Writer.com AI detector	Low	Yes [up to 1200 words]	Yes	Not applicable

AI Detector Reviews

Below, I’ve reviewed each AI detector in detail with hands-on testing, highlighting how it works, accuracy, language support, pricing, etc.

1. ZeroGPT

ZeroGPT is a popular AI content detector. It is capable of detecting GPT-4 and ChatGPT content. Under the hood, ZeroGPT utilizes DeepAnalyse technology with a multi-stage methodology with comprehensive deep learning.

ZeroGPT is free to use, and you can check content up to 15,000 characters (roughly 2500 words on average). That’s generous, and you can use it without the need to sign up for an account. 

So, does it work? In my tests, I found the following:

• Human-written texts → 2.6% AI GPT, mentions it is human-written
• GPT-4-turbo generated text → 89.15 AI GPT, marks it as AI/GPT generated
• GTP-4.5 generated text → 86.83% AI GPT, marks it as AI/GPT generated

From the results, it is easy to see that ZeroGPT works. It is advanced enough to identify the new GPT-4.5 texts with high confidence levels.

As for language support, ZeroGPT supports all languages. They also offer an API for large-scale projects.

ZeroGPT Pricing

ZeroGPT uses a freemium plan with paid plans starting at $7.99 monthly. It offers an ad-free experience with 1,000,000 characters per AI detection and the ability to do 50 batch file checks.

ZeroGPT

2. Originality.ai

Originality.ai’s AI detector helps you detect AI content generated from ChatGPT, Gemini Pro, Llama 3.1, GPT-4o, and other AI content generators or paraphrasing tools.

Unlike ZeroGPT, Originality’s AI detector is not free. I found the walkthrough for new users useful. It uses different color schemes, from green to red, to showcase the confidence of its detection. (Red is 90% confident that the marked sentence is AI-generated, whereas Green is 90% confident that the marked sentence is human-written).

To test Originality.ai, I used its demo content. The image below showcases how Originality.ai displays results.

It highlights sentences with color grading (green for human-written and red for AI-written). (edited).

For languages, it supports 15 languages, including French, Spanish, English, and others. This makes the Originality.ai detector useful for businesses catering to a multi-lingual audience. All the languages have 90% accuracy. 

QuillBot doesn’t offer any API and, hence, is not suitable for enterprise projects.

Originality.ai Pricing

Originality’s AI detector only offers paid plans with pricing starting at $12.95 per month. It offers 2000 credits per month (1 credit = 100 words). You can also take advantage of its pay-as-you-go pricing, where you get 3000 credits for $30 (2-year expiry). The enterprise plan starts at $136.58 per month.

Originality.ai

3. QuillBot

QuillBot is an advanced AI detector that you can use to check work projects, research papers, blog posts, and class assignments.

I personally have used QuillBot multiple times in the past and found it useful in detecting AI content. It marks content in four categories:

• AI-generated (marked as yellow)
• AI-generated & AI-refined (marked as purple)
• Human-written & AI-refined (marked as light blue)
• Human-written (marked as grey)

In my tests, I found QuillBot to deliver constant and accurate results.

• Human-written texts → 0% of the text is likely AI
• GPT-4-turbo generated text → 96% of the text is likely AI
• GTP-4.5 generated text → 96% of the text is likely AI

Impressive results, indeed! As mentioned earlier, Quillbot is my go-to AI detector tool, as it is effective, free, and easy to use.

There is no need to sign up to use QuillBot. Additionally, I found its report useful as it highlights each sentence with the AI usage probability. This gives you the chance to make your copy AI-free by tweaking it a few times.

QuillBot Pricing

QuillBot follows the freemium model (1200 words limit at once), with its paid plans starting at $4.17 per month (annual plan). The premium plan allows unlimited text detection and other features such as paraphrasing, premium grammar, and a plagiarism checker.

QuillBot

4. GPTZero

GPTZero is a ready-to-use AI detector that offers a valuable tool for educators, professionals, and managers.

I found GPTZero to offer advanced features compared to other AI detectors. For example, it comes with a Replay writing feature that can help educators know if the assignment is done manually or via GenAI tools. 

To achieve this, GPTZero offers a Chromium-based plugin. It not only helps scan the document content but also allows the writers to prove that they have done the work.

With 8 million users and 3500 universities and schools, GPTZero is 99% accurate. To verify, I ran my set of texts against it and found the following:

• Human-written texts → Highly confident that the text is human-written
• GPT-4-turbo generated text → Highly confident the text is AI-generated
• GTP-4.5 generated text → Highly confident the text is AI-generated

GPTZero is free to use, with a limit of 5000 characters for every search. There is no signup requirement; however, if you do, you get more free features, such as Advanced sentence sequence, which lets you break down sentences and showcase which part is impacting the AI probabilities.

GPTZero offers multi-lingual support as it supports English, French, and Spanish. All these languages have 90+ accuracy with a 3-5% false positive rate.

GPTZero Pricing

GPTZero follows a freemium plan, with its paid plan starting at $8.33 per month. The Essential plan offers basic AI Scan, which allows you to scan up to 1,50,000 words per month. If you need an Advanced scan, then you need to buy the Premium plan at $12.99 per month.

GPTZero

5. Grammarly AI Detector

Grammarly recently introduced its free AI detector, which detects content from popular AI tools such as Google Gemini, ChatGPT, and Claude.

Like other AI detectors, it showcases the percentage of your text that is AI-generated, enabling you to rewrite those sections for AI-free content. This is useful for content creators as it helps them to manually remove any leftover AI content.

The Grammarly AI detector is free to use. Without sign-up, you can check up to 10,000 characters (roughly 2000-2500 words on average).

In my tests, I found the following:

• Human-written texts → No AI content detected
• GPT-4-turbo generated text → 46% of the text has patterns that resemble AI text (shows 30% if not signed up)
• GTP-4.5 generated text → 96% of the text has patterns that resemble AI texts (same when logged in)

The tests showcase mixed results, especially for GPT-4 turbo text. As you can see below, without logging in, the AI detector detects 30% AI-generated content, whereas it changes to 46%. However, I was not able to replicate similar results for GPT-4.5 texts, which showcase a 96% AI chance (in both instances).

And, when logged in, the results are different.

Note: I am using the Grammarly Pro version. Once you’re logged in, you cannot use AI detection without getting its Pro plan. That’s why I recommend using its free version here. 

Additionally, I like Grammarly as it brings transparency by categorizing text into AI-generated, online sources, or typed by you. It also offers “AI use” citations.

Grammarly only supports the English language and does offer an API for big projects.

Grammarly AI Detector Pricing

Grammarly AI detector pricing starts at $12 per month (Pro plan). Their free plan has a limit of 10,000 characters per search.

Grammarly AI Detector

6. Scribbr

Scribbr helps detect AI content generated by Gemini, GPT4, and ChatGPT.

I’ll not discuss Scribbr in detail because it is Quillbot in disguise. Yes, they offer similar features and use the same AI-detection engine.

I ran the tests to confirm this as well. I know they are similar, as I used both of them during my freelancing career.

At that time, Scribbr utilized a more aggressive AI detection algorithm, which would even mark human-written content as AI. It would make it hard for me to make the content AI-free. However, with time, Scribbr got rid of its algorithm and simply adopted the Quillbot AI detection algorithm, which offered the same features.

So, like Quillbot, you can do unlimited free AI detections up to 1200 words.

Scribbr

7. CopyLeaks

Copyleaks is a trustworthy AI detector. It provides different AI solutions for businesses and governance, offering transparency. One of their products is a free-to-use AI detector.

Copyleaks is an advanced tool with plenty of available options. For example, Copyleaks comes with AI Detection sensitivity. These include:

• Level 1 → directly copied content from LLM, such as ChatGPT
• Level 2 → AI content with minor changes
• Level 3 → AI content that is heavily modified

You can use CopyLeaks for free via its online portal.

As I have directly copied content from LLM, I have set the AI detection sensitivity to 1. You’re free to choose any level based on your needs.

I found Copyleaks to be an effective AI detector. The results are as follows:

• Human-written texts → 0% AI content
• GPT-4-turbo generated text → 100% AI-generated with 77 AI Phrases detected
• GTP-4.5 generated text → 100% AI-generated with 102 AI phrases detected

Not only does Copyleaks detect AI content, but it can also provide useful statistics on how many AI phrases are used. If you sign up, it offers a more detailed report.

Copyleaks AI detector supports 30+ languages, including German, Spanish, English, and others. For large-scale projects, you can take advantage of Copyleaks APIs.

CopyLeaks Pricing

CopyLeaks offers a free-to-use online version for easy detection. It’s paid plan starts at $13.99 (up to 1200 credits). It offers more control and detailed reports with support for multiple languages.

CopyLeaks

8. Undetectable

Undetectable is an advanced AI detector. On its page, it advertises itself as the #1 rated best AI detector by Forbes. However, their claims do not seem to be valid, as I found no supporting evidence. 

Ignoring that, I jumped into its AI detector to find the results correct. 

• Human-written texts → 99% Human, likely 1% AI
• GPT-4-turbo generated text → 1% human, likely 99% AI
• GTP-4.5 generated text → 1% human, likely 99% AI

As you can notice from the above screenshot, it correctly detected the AI content. It can catch content generated from popular Gen AI, including GPTZero, Writer, OpenAI, Sapling, Copyleaks, Quillbot, ZeroGPT, and Grammarly.

Undetectable is free to use with no limits. However, the free version offers the basic feature. The paid advanced feature allows you to convert your AI content to human content. 

Undetectable supports 50+ languages, including Arabic, French, Korean, and English. Developers can integrate Undetectable Check for AI API into custom solutions or for large-scale use.

Undetectable Pricing

Undetectable is free to use. Its paid version starts at $5 per month, which gives you tools to humanize the content and unlimited AI detection.

Undetectable

9. Writer.com AI Detector

Writer.com’s AI detector is a free-to-use detector that lets you check content up to 5,000 words.

I ran the results; I found Write.com’s AI detector to offer a high level of inaccuracy. 

• Human-written texts → 100% human-generated content (True)
• GPT-4-turbo generated text → 88% human-generated content (not True)
• GTP-4.5 generated text → 82% human-generated content (not True)

As you can notice, the results are not all accurate. Clearly, AI detection is not working at all. In that case, I don’t recommend the tool for AI detection.

Writer.com AI Detector

Tips on How to Use AI Detectors Effectively

It’s common to overuse AI detectors, especially for businesses that have received AI-written work without any creativity, originality, or effort.

Google’s stance changed over time. Initially, Google stated that AI-generated content is considered spam. However, Google recently came up with new AI guidelines where AI content is not penalized if it meets Google’s guidelines of E-E-A-T (Expertise, Experience, Authority, Trustworthiness). In short, it must be well-researched, accurate, and useful, and must not manipulate search rankings.

Considering all these, I suggest the following:

• Don’t rely on AI detectors to judge the content. It should be evaluated based on core metrics of research, accuracy, and user intent.
• Always test at least a 1000-word-long text. That’s because smaller content has a high chance of being flagged as AI (false positive), even if it is human-written. I had this experience working with a client who checked human-written content section-wise (200-250 words), leading to a lot of false positives.
• Use more than one AI detector to get rid of any false positives.
• Always let subject-matter experts evaluate content.

Which AI Detector Tool Should I Use?

In this post, I covered 9 AI detectors. However, if I have to pick 2-3 tools, I would suggest the following:

• QuillBot → For its simplicity, accessibility, and accuracy. It is also free to use for up to 1200 words.
• GPTZero → For its advanced set of features via its Chrome plugin. It offers replay writing features and helps document content. I recommend GPTZero for schools and universities.
• CopyLeaks → This is for its accurate AI detection and the ability to showcase the AI phrases detected metric. It offers excellent AI detection capabilities for enterprise use.

The only AI detector that doesn’t offer free AI checks is Originality.ai’s AI detector. That’s why I recommend it for large-scale publications that want the best AI detector and don’t mind paying.

Can AI Detect AI Content?

Yes, AI can detect AI content. 

To test it, I went ahead and checked AI-generated content in ChatGPT and Gemini.

All you need to do is ask the Gen AI to act as an AI detector. Also, tell me to showcase the probability of the content being AI-generated. The prompt for achieving this is as follows:

“Hi, please act as an AI detector. Your task is to detect if the content that I share is AI-generated or not. You should also showcase the probability of AI-generated content in terms of % (0-100).”

I checked the GPT 4.5 text, and ChatGPT mentioned the probability of AI-generated content as 82%. Not bad at all!

Now, let’s check it against human-generated content.

ChatGPT listed the human-written content as having a 21% chance of AI-generated content. That’s high compared to other dedicated AI content checkers. 

Similarly, you can trick Gemini to act as an AI detector.

For this purpose, I used the Gemini 2.0 Flash version. The results are as follows:

• Human-written text → 92% probability as generated by AI.
• GPT 4.5 text → 8% probability as generated by AI.

That’s completely surprising, as Gemini fails as an AI detector.

In short, AI can detect AI content but with a lesser degree of accuracy. ChatGPT did it with fair accuracy, but Gemini failed in this task.

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