Best AI Detectors in 2025: We Tested 20+ Tools to Find Which Ones Work Best

How AI Detectors Work

AI detectors look at how text is written to work out whether it was written by a human or a computer.

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These tools look at how sentences are put together, what words are used, and how easy it is to guess what will happen next in the text, and how well the writing flows.

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The technology behind most detectors relies on two main ideas:

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• Perplexity
• Bursitness

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Here’s what they mean:

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Perplexity

Perplexity measures how predictable your text is. AI-generated content usually scores lower on perplexity because language models tend to choose words that are likely to appear in the text. Human writing is more unpredictable and includes more creative word choices.

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Burstiness

Burstiness tracks variation in sentence length and structure. AI tends to write sentences that are all the same length, but human writers mix short and long sentences.

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Most detectors give a probability score to show whether text is human or machine-generated. But no tool is 100% accurate, so you should treat the results as educated guesses rather than definitive conclusions.

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Also read: How to bypass AI detection — we tested 10 of the best AI Humanizers.

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The best AI Detectors Compared

To help you decide which AI detector is best, below is a summary of how each tool compares to its competitors:

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Now, let's take a closer look at each one:

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Overchat AI Detector

Overchat AI Detector is a free tool that can identify text generated by various AI models, such as GPT-5, Claude and Gemini, and many others.

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Here’s how it works: The detector looks for repetitive patterns and overused AI phrases and grammatical constructs to work out if the content was created by a language model.

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Then, you get a confidence score ranging from 0% (fully human) to 100% (definitely AI-generated), as well as a breakdown of why that is.

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Key features:

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• Detects text from ChatGPT, Claude, Gemini, and other popular models
• Provides detailed insights showing which phrases and sentence structures triggered detection
• Completely free with no signup required
• No word limit restrictions
• Instant results with percentage-based confidence scoring

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How it works:

To use Overchat AI, it is very simple:

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1. Paste your text into the analyzer
2. Click Analyze Text

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Overchat will study the writing patterns and characteristics that are unique to different AI models. It will then provide a detailed report explaining why specific elements suggest that something has been created by an AI.

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Pricing: Completely free with 5 checks and no signup required

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Best for: Best for: Writers who want to test AI-assisted content before publication, verify whether freelance work was AI-generated, or prevent their own writing from triggering false positives on other detection tools.

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QuillBot

QuillBot is a popular AI detector that also includes multiple writing features: grammar checking, paraphrasing, and text humanization.

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This tool can spot copy written by all major language models and highlights sections that appear AI-generated. You can scan up to 1,200 words at a time without creating an account.

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Key features:

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• Accurate detection of AI-generated text with sentence-level breakdown
• Built-in humanizer to rewrite AI content in a more natural style
• Grammar checker and paraphrasing tool included
• Plagiarism detection available in premium plans
• Citations generator and summarizer tools

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How it works:

Using QuillBot is straightforward:

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1. Go to the AI Detector section
2. Paste your text (up to 1,200 words for free users)
3. Click Detect AI

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Pricing: Free for basic detection (1,200 words). Premium starts at $4.17/month (billed annually) with unlimited paraphrasing and advanced features.

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Winston AI

Winston AI is an AI detection tool that claims 99.98% accuracy and includes features for both text and image analysis. It also offers a unique certification called HUMN1 that proves your content is human-generated.

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Key features:

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• High accuracy rate for detecting AI-generated content
• Image scanning to identify AI-generated visuals
• Plagiarism checker included in all plans
• AI prediction map showing which sections triggered detection
• HUMN1 certification for your website or blog
• Integration with WordPress and XML sitemaps

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How it works:

To use Winston AI:

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1. Sign up for a free account (you get 2,000 credits to start)
2. Paste your text or upload a document
3. Click Check AI score

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Pricing: Free trial with 2,000 credits (1 credit = 1 word). Paid plans start at $12/month for the Essential plan with 80,000 words per month.

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Originality.AI

Originality.AI is an AI detection tool built for content publishers and marketing teams who manage large volumes of content.

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The platform combines AI detection with plagiarism checking and readability analysis, making it a comprehensive solution for content quality control. It's particularly popular among SEO agencies and content teams who need to scan multiple articles quickly.

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Key features:

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1. Detection for ChatGPT, Claude, Gemini, and other major models
2. Plagiarism checker with detailed source matching
3. Readability scoring and analysis
4. Chrome extension for easy integration
5. Bulk scanning for multiple documents
6. Team collaboration features with shareable reports

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How it works:

To use Originality.AI:

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1. Create an account (requires credit card for free trial)
2. Paste your text, upload a file, or enter a URL
3. Click Scan

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The tool provides both AI detection and plagiarism results in one report. You can download PDF reports or share links with clients or team members.

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Pricing: Pay-as-you-go model at $0.01 per 100 words, or subscription plans starting at $14.95/month (billed annually) for 20,000 words.

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GPTZero

GPTZero is one of the most popular free AI detectors, offering a generous word limit and detailed analysis without requiring payment.

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The tool was designed specifically for educators but has expanded to serve writers, researchers, and content creators. GPTZero provides both basic and advanced scanning options with clear visual breakdowns of detection results.

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Key features:

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• Free plan with up to 10,000 words per month
• Advanced scan option highlighting AI-generated sentences
• AI vocabulary tool showing commonly used AI phrases
• Source verification to check claims in documents
• Plagiarism scanning (premium plans only)
• Support for multiple file formats including PDF and Word

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How it works:

To use GPTZero:

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1. Visit the website and select your role (student, educator, writer, or reviewer)
2. Sign up with Google or email
3. Paste text or upload a file
4. Click Scan for AI

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GPTZero color-codes your text, highlighting sections that appear AI-generated in yellow and likely human-written sections in green.

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You also get an overall probability score and detailed sentence-by-sentence analysis.

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Pricing: Free plan with 10,000 words/month. Premium plans start at $10/month (billed annually) with increased limits and plagiarism detection.

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Pangram Labs

Pangram Labs is an AI detection tool that has been reviewed by the University of Maryland and is trusted by major platforms like Quora.

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The platform offers unique features like an AI phrases tool and side-by-side text comparison, making it useful for both detection and content analysis.

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Key features:

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• AI phrases tool that highlights commonly used LLM expressions
• Side-by-side text comparison to spot similarities
• Plagiarism detection included
• Integration with Google Classroom and Canvas
• Chrome extension available

How it works:

To use Pangram Labs:

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1. Sign up for an account
2. Paste your text or upload a document
3. Select which tools to run (AI detection, plagiarism, etc.)
4. Click Run Selected Scans

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The tool provides color-coded results showing which sections triggered AI detection.

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Pricing: Individual plan at $12.50/month with 600 AI scans. Professional plan at $37.50/month with 3,000 scans. Educational institutions get special pricing at $5/month with unlimited checks.

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Detecting-AI

Detecting-AI goes beyond basic AI detection to include fact-checking, plagiarism detection, and various SEO tools.

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The platform supports multiple languages including French, Spanish, Russian, German, Portuguese, and Arabic, making it useful for international content creators, and offers API access for developers who want to integrate detection into their own workflows.

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Key features:

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• Multi-language support for 7+ languages
• AI humanizer to rewrite flagged content
• Plagiarism checker and fact-checker
• SEO tools like grammar checker and paragraph generator
• API access for integration
• Browser extension available

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How it works:

To use Detecting-AI:

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1. Visit the website (no signup required for basic detection)
2. Paste your text or upload a file (.txt, .doc, .docx, or PDF)
3. Click Detect AI

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The tool provides a percentage score showing how much of your text appears AI-generated. You can then use the built-in humanizer to rewrite problematic sections.

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Pricing: Free plan with 5,000 characters per scan. Yearly plan at $7/month (50% off promotional pricing) with 12,000 plagiarism credits and unlimited daily scans.

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Smodin

Smodin is another AI detection tool that includes grammar checking and rewriting, which is useful if you want  to polish your content while checking for AI.

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The platform offers a simple UI and detection results are easy to understand.

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However, the big issue with the tool is the fact that their free tier is quite limited compared to competitors.

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Smodin claims to detect text from ChatGPT, Gemini, and Azure AI models.

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Key features:

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• AI detection with grammar checking
• Text improvement suggestions
• Support for multiple AI model detection
• API access for developers (paid plans)
• Simple, easy-to-use interface
• Weekly usage limits on free plan

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How it works:

To use Smodin:

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1. Visit the AI detector page
2. Paste your text (up to 5,000 characters)
3. Click Detect AI

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You’ll get an AI probability score, but, unlike some competitors, Smodin doesn't provide detailed sentence-by-sentence breakdowns.

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Pricing: Free plan with 5,000 characters per text and 5 uses per week. Essentials plan at $12/month (or $15/month billed monthly) with 15,000 characters per text and unlimited daily uses.

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How to Choose the Right AI Detector

Not every detector does the same job. Choose based on what you need and what you’re willing to pay.

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Match the tool to your job

While some tools come with built-in plagiarism detection, rewriting features, and in-depth linguistic analysis, consider whether you really need all that. It can be tempting to go for the most feature-packed option, but if you mainly need to check multiple texts quickly, a more complex interface might just slow you down — and you could end up paying for features you never use.

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Test the Free Plan Before You Commit

Spend some time with the free version before paying — it’s the quickest way to see whether the tool’s approach to detection makes sense for the kind of writing you handle.

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Compare pricing by your usage.

The cost structure can differ just as much as the features. The most popular pricing models are:

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• Per scan
• Per word
• Monthly subscriptions
• Completely free

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Per-scan or per-word pricing works best if you only need to run checks occasionally — for example, when verifying a few freelancer submissions or testing short samples.

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Monthly subscriptions make more sense for regular use, such as teachers checking assignments or editors reviewing batches of content. These plans often include unlimited scans or higher usage limits, which quickly outweigh the cost if you’re running checks every day.

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Free tools can be surprisingly capable, especially for basic detection, but some limit word count or hide parts of the results.

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Test accuracy on your own text

Before relying on any detector’s claims, run a few tests. Feed in both AI-generated text and your own writing to see how it handles nuance, tone, and variation. Accuracy can differ dramatically between tools, and the only way to know if one fits your type of content is to test it directly.

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Common Use Cases for AI Detectors

AI detectors serve different purposes depending on who's using them. Here are the most common scenarios where these tools prove useful:

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For Educators

With tools like ChatGPT becoming widespread in schools, teachers need a way to spot when students submit AI-generated essays, so many schools now require instructors to run suspicious submissions through detection tools.

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For agencies and publishers

If you’re hiring freelance writers, you need to confirm they're getting human-written content as promised. Some freelancers use AI to speed up their work without disclosing it, which can create legal and quality issues for the client. A quick scan before publication helps catch this early.

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For writers

Even if you don’t use AI, you may worry about false positives. Sometimes human writing triggers detection algorithms, especially if you have a straightforward style or write about technical topics. That’s why, testing your own work before submission helps you identify and rework sections that might get flagged.

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For SEO professionals

Google has stated that AI content isn't automatically penalized, but low-quality AI content can hurt rankings. SEO teams use detectors to audit existing content and check new articles before publishing, especially when working with multiple writers or agencies.

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For businesses

Companies that publish content under their brand name want to ensure it meets quality standards. AI-generated content can contain factual errors, so detection tools help maintain consistency and catch problems before they go live.

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For researchers and journalists

AI-generated text can include fabricated citations, made-up statistics or misinformation stated with confidence. This is why researchers and journalists use detection tools as an initial filter when evaluating sources or checking whether quoted material might be artificially generated.

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FAQs

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What is an ai detector?

An AI detector is a tool that analyzes text to determine whether it was written by a human or generated by an artificial intelligence model like ChatGPT, Claude, or Gemini. These tools examine writing patterns, sentence structure, word choice predictability, and other linguistic features to make this determination, then provide a probability score indicating how likely the content is AI-generated.

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How does an AI detector work?

AI detectors work by analyzing two main factors: perplexity and burstiness. Perplexity measures how predictable the text is — AI tends to choose statistically likely words, making it more predictable than human writing.

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Burstiness tracks variation in sentence length and structure—AI typically produces uniform sentences while humans naturally mix short and long ones. The detector combines these measurements with pattern recognition to estimate whether content is human or machine-generated.

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What is the best AI detector overall?

We recommend Overchat AI Detector as the best overall option because it's completely free, has no word limits, requires no signup, and detects text from all major AI models including ChatGPT, Claude, and Gemini.

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What is the best AI detector for teachers?

The best AI detector for teachers is Winston AI or Turnitin, because they offer high accuracy (99.98% for Winston), include plagiarism checking, and provide detailed reports that can be shared with students or administrators.

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What is the best AI detector for students?

Students should also use Winston AI for the same reasons it works well for teachers. The free trial offers 2,000 credits to test the tool, and the detailed breakdowns help students learn which writing patterns to avoid if they want their legitimate work to pass detection.

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What ai detector do teachers use?

Most teachers use Turnitin, which is integrated directly into learning management systems like Canvas and Blackboard.

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Turnitin combines plagiarism detection with AI detection, making it convenient for educators who are already using it for assignment submissions. The tool is specifically designed for educational institutions and includes features for grading and providing feedback alongside detection results.

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How to get past an AI detector?

The most reliable way to pass AI detectors is to rewrite AI-generated content by hand, focusing on breaking typical AI patterns. Here’s how:

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• Add personal anecdotes
• Vary your sentence length
• Include specific facts and statistics with sources
• Use contractions and casual phrasing where appropriate
• Introduce intentional stylistic quirks.

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Humanizer tools can also help to rewrite AI generated text, though this way is not as bullet-proof as rewriting by hand.

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Should You Use an AI Detector?

The short answer: absolutely yes — especially since many of these tools are completely free, or at least offer free trials, which are usually enough for occasional use.

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• If you’re a writer, it’s incredibly useful to know whether your text gets flagged as AI-generated — even if it was only AI-assisted — or if there are any false positives.
• If you’re an editor, teacher, or business, these tools can help you check whether the content provided by freelancers or team members was AI-assisted or fully AI-generated (which isn’t always a bad thing, but it’s a problem if the content is AI-generated and low quality).

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Who shouldn’t use AI detectors?

Well, if you’re creating your copy entirely with AI, you probably don’t need a detector — you already know what kind of score you’re going to get. 🙂

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