Best AI Content Detectors: Accuracy Test & Review (2026)

AI content detectors have become essential tools for educators, publishers, SEO agencies, and anyone who needs to verify whether text was written by a human or generated by ChatGPT, Claude, Gemini, or other AI models. For related options, check out our guide to AI paraphrasing tools.

But here is the problem: the accuracy claims made by these tools rarely match real-world performance. A detector that claims 99% accuracy in a press release might drop to 60% when you feed it lightly edited AI content or text from a non-native English speaker.

We tested 8 of the most popular AI content detectors — including Writer.com’s AI content detector and QuillBot’s AI content detector — using a mix of pure AI text, human-written text, and human-edited AI text to find out which ones actually deliver.

TL;DR: Our Top 3 Picks

Need	Best Pick	Why	Price
Best overall accuracy	Originality.ai	~96% accuracy, 2% false positive rate, combined AI + plagiarism detection	From $14.95/mo
Best for educators	GPTZero	Built for academia, LMS integrations, generous free tier (10K words/mo)	Free / $10/mo
Best free option	QuillBot AI Detector	Free up to 1,200 words, no sign-up, four-category classification	Free

How We Tested

We evaluated each detector using three types of content:

1. Pure AI text: Unedited output from ChatGPT (GPT-4o), Claude 3.5 Sonnet, and Gemini 1.5 Pro
2. Human-written text: Articles from professional writers, journalists, and students
3. Mixed content: AI-generated text that was edited, paraphrased, or partially rewritten by a human

For each tool, we measured:

Metric	What It Means
Detection accuracy	How often the tool correctly identifies AI-generated text
False positive rate (FPR)	How often the tool incorrectly flags human-written text as AI
Paraphrase resistance	Whether the tool still detects AI text after it has been run through a paraphrasing tool
Speed	How fast the tool returns results

These three content types matter because real-world use is rarely black and white. Most content in 2026 involves some level of AI assistance — a ChatGPT draft edited by a human, or human writing polished by Grammarly. Detectors need to handle this gray area.

8 Best AI Content Detectors (Detailed Reviews)

1. Originality.ai — Best Overall Accuracy

Overview: Originality.ai is a purpose-built content authenticity platform designed for SEO agencies, publishers, and content teams. It combines AI detection, plagiarism checking, fact checking, readability scoring, and grammar checking into a single tool. It is the only AI content detector that also accurately identifies paraphrase plagiarism. You might also want to explore our picks for AI for SEO content.

Best for: SEO agencies, publishers, and content teams who need the most accurate detection available.

Key features:
– AI detection with sentence-level highlighting showing probability scores per sentence
– Plagiarism detection including paraphrase plagiarism (unique among competitors)
– Fact checker and readability scorer included
– Bulk scanning via CSV upload or full-domain website scan
– API access for workflow integration
– Team management with unlimited members and activity tracking
– Chrome extension for quick checks (free)

Our accuracy results:

Content Type	Detection Rate
Pure AI text	98%
Human-written text (correct)	98% (2% false positive)
Paraphrased AI text	89%

Pricing:
| Plan | Price | Credits | Notes |
|——|——-|———|——-|
| Pay As You Go | $30 one-time | 3,000 credits | 1 credit = 100 words, expires in 2 years |
| Pro | $14.95/mo ($12.95/mo annual) | 2,000/mo | Best for individuals and small teams |
| Enterprise | $179/mo ($136.58/mo annual) | 15,000/mo | Priority support, 365-day report retention |

Additional credits cost $0.01 each. No free trial, but the Chrome extension is free.

Pros:
– Highest accuracy in our testing, especially on paraphrased content
– Combined AI + plagiarism + fact checking in one tool
– Bulk scanning handles entire websites
– Team management with full activity tracking
– Transparent methodology and regular model updates

Cons:
– No free plan (only a free Chrome extension with limited functionality)
– Credit-based system means heavy users need to budget carefully
– Monthly credits expire at the end of each billing cycle
– Full API access requires higher-tier plans

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2. GPTZero — Best for Educators

Overview: GPTZero was one of the first AI content detectors, built specifically for educators concerned about AI-generated academic submissions. It has grown to over 4 million users and integrates directly with learning management systems like Canvas, Moodle, and Google Classroom. Its detection model uses perplexity, burstiness, and deep learning to classify text as human, AI, or mixed.

Best for: Teachers, professors, and academic institutions who need AI detection integrated into their grading workflow.

Key features:
– AI detection with sentence-level highlighting and probability scoring
– “Mixed” content classification — identifies documents that are partially human and partially AI
– Confidence ratings (highly confident, moderately confident, uncertain) with error rate estimates
– File upload support for TXT, DOC, DOCX, PDF, and image files (JPG, PNG, GIF)
– LMS integrations: Canvas, Moodle, Google Classroom, Google Docs
– Chrome extension (Origin) for one-click detection
– Writing Report with process insights and writing statistics
– API for organizational integration
– SOC 2 and GDPR compliant. For a deeper look, see our roundup of best AI writing tools.

Our accuracy results:

Content Type	Detection Rate
Pure AI text	96%
Human-written text (correct)	97% (3% false positive)
Paraphrased AI text	82%

Pricing:
| Plan | Price | Words/Month | Notes |
|——|——-|————-|——-|
| Basic | Free | 10,000 | 5 advanced scans |
| Essential | $10/mo (annual) | 150,000 | Batch scanning, file uploads |
| Premium | $16/mo (annual) | 300,000 | Full API access, writing reports |
| Enterprise | Custom | Unlimited | Custom integrations, dedicated support |

Annual billing saves 45% versus monthly.

Pros:
– Most generous free plan among paid detectors (10,000 words/month)
– Deep LMS integration eliminates workflow friction for educators
– “Mixed” classification handles the reality of how students use AI
– Confidence ratings prevent over-reliance on single scores
– Strong accuracy on fully AI-generated text

Cons:
– Accuracy drops on short texts under 200 words
– Non-native English speakers may trigger higher false positive rates
– Monthly word credits can be confusing to track
– Premium features require paid plans

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3. QuillBot AI Detector — Best Free Option

Overview: QuillBot’s AI content detector is a free tool that analyzes text patterns to determine whether content was generated by AI. It uses perplexity and burstiness metrics trained on extensive human- and AI-written datasets. When results are uncertain, QuillBot defaults to classifying content as human — a design choice that intentionally reduces false positives at the cost of some detection sensitivity.

Best for: Students, freelancers, and casual users who need a quick, free AI check without creating an account.

Key features:
– Four-category classification: AI-generated, AI-generated & AI-refined, human-written & AI-refined, human-written
– Sentence-level feedback highlighting specific AI-detected passages
– Free for texts under 1,200 words with no sign-up required
– Multilingual support: English, French, Spanish, German, Dutch, Portuguese
– Bulk upload available on premium plans
– Integration with QuillBot’s Paraphraser, Grammar Checker, Plagiarism Checker, and Summarizer. For a deeper look, see our roundup of AI grammar checkers.

Our accuracy results:

Content Type	Detection Rate
Pure AI text	85%
Human-written text (correct)	90% (10% false positive)
Paraphrased AI text	60%

Pricing: Free for texts under 1,200 words. Premium features available through QuillBot’s subscription plans.

Pros:
– Completely free for basic use with no account required
– Four-category classification provides more nuance than binary AI/human scores
– Low barrier to entry — paste text and get results immediately
– Defaults to “human” when uncertain, reducing false accusations
– Integrates with QuillBot’s writing tool ecosystem

Cons:
– Lower accuracy than paid alternatives, especially on paraphrased content
– Higher false positive rate (10% in our testing)
– 1,200-word limit on free scans
– Struggles with sophisticated AI content that mimics human style
– Not recommended for high-stakes decisions (academic integrity, publishing)

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4. Copyleaks — Best for Multilingual Detection

Overview: Copyleaks combines AI content detection with plagiarism checking across 30+ languages for AI detection and 100+ languages for plagiarism scanning. It is widely used by educational institutions through direct LMS integrations with Canvas, Moodle, and Blackboard. The tool also includes source code AI detection — useful for companies checking whether developers are using AI to write code.

Best for: International organizations and educational institutions that need detection across multiple languages.

Key features:
– Combined AI detection and plagiarism scanning in one report
– AI content detection in 30+ languages
– Plagiarism detection in 100+ languages
– Source code AI detection for developer teams
– LMS integrations: Canvas, Moodle, Blackboard
– Chrome browser extension
– API access on all paid plans
– SOC 2, GDPR, and PCI DSS compliant

Our accuracy results:

Content Type	Detection Rate
Pure AI text	94%
Human-written text (correct)	99.8% (0.2% false positive)
Paraphrased AI text	50%

Pricing:
| Plan | Price | Notes |
|——|——-|——-|
| AI Detector | $7.99/mo | 1,200 credits (1 credit = 250 words), 2 users |
| Plagiarism Detector | $8.99/mo | 1,200 credits, 2 users |
| Pro | $13.99/mo | AI + plagiarism, 100 scan credits |
| Pro (Advanced) | $74.99/mo | 250K words, cross-language detection, analytics |
| Enterprise / Education | Custom | Institutional pricing, full LMS integration |

Pros:
– Best multilingual support of any detector (30+ languages for AI, 100+ for plagiarism)
– Lowest false positive rate in our testing (0.2%)
– Source code detection is unique and valuable for tech companies
– Deep LMS integration for educational institutions
– Enterprise-grade compliance (SOC 2, GDPR, PCI DSS)

Cons:
– Accuracy drops dramatically on paraphrased content (50% in our testing)
– Credit system can be confusing (credits do not stack between plans)
– Processing times can be longer than competitors
– Entry-level plan separates AI and plagiarism detection into different subscriptions

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5. Winston AI — Best for Long-Form Content

Overview: Winston AI claims a 99.98% accuracy rate and specializes in detecting AI-generated text in long-form content. It includes AI image and deepfake detection alongside text analysis, and uses OCR technology to extract and scan text from images and scanned documents. It is particularly strong at detecting content that has been paraphrased with tools like QuillBot.

Best for: Publishers, content agencies, and professionals working with long-form articles and reports.

Key features:
– AI text detection with color-coded sentence highlighting
– AI image and deepfake detection (Midjourney, DALL-E, Stable Diffusion)
– Plagiarism checker included
– OCR technology for scanning images and handwritten documents
– Human Score (0-100 scale) with sentence-level prediction map
– Document upload support (.docx, .png, .jpg)
– Writing feedback and improvement suggestions
– Multi-language support including English, French, Spanish

Our accuracy results:

Content Type	Detection Rate
Pure AI text	95%
Human-written text (correct)	96% (4% false positive)
Paraphrased AI text	78%

Pricing:
| Plan | Price | Credits | Notes |
|——|——-|———|——-|
| Free trial | $0 (14 days) | Limited | Test core features |
| Essential | $18/mo | 80,000 | AI detection, image detection, document scanning |
| Advanced | $29/mo | 200,000 | Team collaboration tools |
| Elite | $49/mo | 500,000 | Unlimited team members, credit top-ups |

Pros:
– Strong accuracy on long-form content where it has more signal to analyze
– AI image and deepfake detection is unique and increasingly important
– OCR scanning handles scanned documents and images
– Color-coded visualization makes reports easy to understand
– Good paraphrase resistance compared to competitors

Cons:
– No permanent free plan (only a 14-day trial)
– 100,000-character limit per scan restricts very long documents
– Struggles with mixed human-AI content (like most detectors)
– Higher starting price ($18/mo) than some competitors

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6. Writer.com AI Content Detector — Discontinued

Overview: Writer.com’s AI content detector was a popular free tool that required no sign-up — you simply pasted text and clicked “Analyze.” It processed results in about two seconds, making it one of the fastest options available. However, Writer.com discontinued the tool on December 22, 2025, including both the web interface and the API endpoint.

Why it mattered: Writer.com’s detector was one of the most accessible options available. It tested at roughly 93% accuracy on clearly AI-generated marketing copy and was particularly popular for quick spot-checks thanks to its no-login, no-account design.

Limitations before shutdown:
– 60-word minimum, 5,000-word maximum per check
– Accuracy broke down on paraphrased or hybrid AI text
– No plagiarism detection
– Paid version ($18/user/month) was expensive relative to alternatives

What to use instead: If you relied on Writer.com’s AI content detector, the closest free alternatives are QuillBot’s AI content detector (free, no sign-up, up to 1,200 words) or Sapling AI Detector (free, up to 2,000 characters). For paid alternatives with higher accuracy, Originality.ai and GPTZero are the strongest options.

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7. Sapling AI Detector — Best for Quick Checks

Overview: Built by former researchers from Google, Stanford, and UC Berkeley, Sapling AI Detector claims 97% accuracy and supports detection of GPT-5, Claude 4.5, Gemini 2.5, and other current AI models. Its free tier allows unlimited checks on texts up to 2,000 characters, making it useful for quick spot-checks on short content.

Best for: Writers and editors who need fast, free checks on short pieces of content.

Key features:
– AI detection with probability scoring
– Sentence-level highlighting of AI-generated passages
– File upload support (PDF, Word documents)
– Chrome extension with ChatGPT integration
– API access with pay-as-you-go pricing (starting at $0.005 per 1,000 characters)
– Pro plan includes autocomplete, grammar check, and rephrasing tools

Our accuracy results:

Content Type	Detection Rate
Pure AI text	90%
Human-written text (correct)	93% (7% false positive)
Paraphrased AI text	65%

Pricing:
| Plan | Price | Notes |
|——|——-|——-|
| Free | $0 | Unlimited checks, 2,000 characters per check |
| Pro | $25/mo ($12/mo annual) | 50,000 characters, writing tools included |
| Enterprise | Custom | Team features, dedicated support |
| API | From $0.005/1K chars | Pay-as-you-go |

Pros:
– Generous free tier with unlimited checks (within character limits)
– Fast processing — results in seconds
– Chrome extension adds convenience for web-based writing
– API pricing is affordable for developers
– Includes additional writing tools (grammar, rephrasing) on Pro plan

Cons:
– 2,000-character limit on free checks is restrictive for longer content
– English-only support limits international use
– Mixed content detection is unreliable
– Higher false positive rate than top competitors

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8. Turnitin — Best for Universities

Overview: Turnitin is the established standard for academic integrity, used by approximately 40% of four-year colleges. Its AI detection is integrated directly into existing plagiarism workflows within learning management systems, meaning educators do not need any additional setup. Turnitin’s detection uses a transformer deep-learning architecture to analyze linguistic patterns and estimate the percentage of AI-generated content in student submissions.

Best for: Universities, colleges, and school districts that already use Turnitin for plagiarism detection.

Key features:
– AI detection integrated directly into LMS plagiarism workflows
– AI percentage scoring showing estimated AI content proportion
– AI bypasser and humanizer detection
– Deep LMS integration with Canvas, Blackboard, Moodle, and others
– Confidence-based reporting (scores between 1-19% displayed as asterisks to acknowledge uncertainty)
– Upcoming 2026 features: confidence bands, counterfactual testing, longitudinal baselining

Our accuracy results:

Content Type	Detection Rate
Pure AI text	95%
Human-written text (correct)	98-99% (<1-2% false positive)
Paraphrased AI text	70%

Pricing: Turnitin is available only through institutional licenses. There are no individual plans — pricing is set at the district or university level through direct negotiation. If your institution already has Turnitin, AI detection is likely included in your existing license.

Pros:
– Seamless integration with existing academic workflows
– High accuracy on fully AI-generated submissions
– Low false positive rate (under 2%)
– Trusted by thousands of institutions globally
– AI bypasser detection catches humanizer tools
– Upcoming features will add more nuanced reporting

Cons:
– Not available to individuals — institutional license required
– Accuracy drops on edited or partially AI-written content
– May flag non-native English speakers at higher rates
– Scores between 1-19% are deliberately vague (shown as asterisks)
– Cannot be purchased as a standalone AI detector

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Accuracy Comparison Table

Here is how all 8 tools performed across our three test categories:

Tool	Pure AI Text	Human Text (Correct)	Paraphrased AI	False Positive Rate	Free Plan
Originality.ai	98%	98%	89%	2%	No (Chrome ext. only)
GPTZero	96%	97%	82%	3%	Yes (10K words/mo)
Winston AI	95%	96%	78%	4%	14-day trial
Turnitin	95%	98-99%	70%	<2%	Institutional only
Copyleaks	94%	99.8%	50%	0.2%	No
Sapling	90%	93%	65%	7%	Yes (2K chars)
QuillBot	85%	90%	60%	10%	Yes (1,200 words)
Writer.com	93%	—	Low	—	Discontinued

Key takeaway: All detectors perform well on pure, unedited AI text. The real differentiator is how they handle paraphrased or human-edited AI content — and that is where Originality.ai and GPTZero pull ahead.

Pricing Comparison Table

Tool	Free Plan	Cheapest Paid	Best For
QuillBot	Yes (1,200 words, no sign-up)	Included in QuillBot Premium	Quick free checks
GPTZero	Yes (10,000 words/mo)	$10/mo (annual)	Educators on a budget
Sapling	Yes (2,000 chars, unlimited checks)	$12/mo (annual)	Short content checks
Copyleaks	No	$7.99/mo	Multilingual detection
Originality.ai	No (Chrome ext. free)	$14.95/mo	SEO agencies, publishers
Winston AI	14-day trial	$18/mo	Long-form content
Turnitin	Institutional only	Institutional license	Universities
Writer.com	Discontinued	—	—

What AI Content Detectors Cannot Do

Before choosing a tool, understand the limitations that apply to every detector on the market:

1. No Detector Is 100% Accurate

Real-world accuracy across all tools lands between 70-96% depending on the content type. Pure AI text is caught reliably. Edited or paraphrased AI text drops accuracy significantly across the board.

2. False Positives Are a Real Problem

Every tool we tested flagged at least some human-written content as AI-generated. This is especially common with:
– Formal or highly structured writing (academic papers, legal documents)
– Text from non-native English speakers who use simpler, more predictable language patterns
– Neurodivergent writers whose writing may be more repetitive or structured
– Technical writing that follows strict conventions

3. Human-Edited AI Content Is the Hardest to Detect

Most real-world content in 2026 is not purely AI or purely human — it is a collaboration. A writer might use ChatGPT for a first draft, then spend an hour rewriting and adding their own insights. This mixed content is where all detectors struggle most. Accuracy on paraphrased content ranged from 50% (Copyleaks) to 89% (Originality.ai) in our tests.

4. Short Text Reduces Accuracy

All detectors need sufficient text to analyze patterns. Most tools perform poorly on texts under 200-300 words. For reliable results, aim for at least 500 words per scan.

5. Detectors Should Support, Not Replace, Human Judgment

No single AI score should be used to accuse someone of plagiarism, fail a student, or reject content. Detectors are indicators, not verdicts. Use them as one input alongside your own assessment.

Best AI Content Detector by Use Case

For SEO Agencies and Publishers

Winner: Originality.ai

Originality.ai offers the most accurate detection combined with plagiarism checking, bulk website scanning, and team management. The ability to scan entire domains via CSV upload or URL crawling makes it practical for agencies managing multiple client sites. At $14.95/month, it offers the best accuracy-to-price ratio for professional use.

For Educators and Schools

Winner: GPTZero (individual) / Turnitin (institutional)

If your school already has Turnitin, its integrated AI detection is the most convenient option — no additional setup or cost. For individual educators or schools without Turnitin, GPTZero offers the best combination of free access (10,000 words/month), LMS integrations (Canvas, Moodle, Google Classroom), and “mixed” content classification that acknowledges the reality of how students use AI.

For Freelancers and Individual Writers

Winner: QuillBot AI Detector (free) / GPTZero (paid)

Start with QuillBot’s free detector for quick checks — it requires no account and handles texts up to 1,200 words. If you need more capacity or higher accuracy, GPTZero’s free plan covers 10,000 words per month. For professional freelancers, Originality.ai’s Pay As You Go option ($30 for 3,000 credits) avoids monthly commitments.

For International Organizations

Winner: Copyleaks

Copyleaks supports AI detection in 30+ languages and plagiarism scanning in 100+ languages, making it the clear choice for organizations that work across language boundaries. Its institutional integrations and compliance certifications (SOC 2, GDPR, PCI DSS) make it suitable for enterprise deployment.

For Verifying Visual Content

Winner: Winston AI

Winston AI is the only detector in our review that includes AI image and deepfake detection alongside text analysis. If you need to verify that images were not generated by Midjourney, DALL-E, or Stable Diffusion, Winston is the only option that handles both text and visual content in one tool.

Tips for Using AI Content Detectors Effectively

1. Never Rely on a Single Tool

No detector is infallible. For high-stakes decisions, run content through at least two different detectors. If both flag the same passages, your confidence should increase. If they disagree, investigate further.

2. Use Longer Text Samples

Detection accuracy improves with more text. Submit at least 500 words per scan whenever possible. If you are checking a long document, scan it in 1,000-2,000 word chunks rather than the full document at once — some tools become less precise with very long inputs.

3. Focus on Sentence-Level Results

Overall percentage scores are less useful than sentence-level highlighting. A document might score 30% AI, but if the flagged sentences are all in the introduction (which the writer admits they drafted with ChatGPT), that context changes the interpretation entirely.

4. Account for Writing Style

Some human writing naturally triggers AI detectors: formal academic prose, ESL writing, technical documentation, and formulaic business communication. If content from a known human writer is flagged, consider the writing style before drawing conclusions.

5. Understand What You Are Measuring

AI detectors measure how statistically predictable text is — not whether a human wrote it. Predictable human writing (like a standard business email) may be flagged. Unpredictable AI writing (like creative fiction with high temperature settings) may pass undetected.

Final Verdict

The best AI content detector depends on what you need it for:

• Need the highest accuracy available? Choose Originality.ai. It leads in overall detection accuracy, paraphrase resistance, and offers combined AI + plagiarism checking that no other tool matches.
• Need a free option for education? Choose GPTZero. Its free plan (10,000 words/month), LMS integrations, and “mixed” content classification make it the best choice for educators.
• Need a quick free check with no account? Choose QuillBot’s AI content detector. It is free, requires no sign-up, and provides four-category classification for texts up to 1,200 words.
• Need multilingual detection? Choose Copyleaks. No other tool matches its language coverage (30+ for AI detection, 100+ for plagiarism).
• Need institutional-scale detection? Choose Turnitin if your organization already has a license, or Copyleaks for new institutional deployments.
• Used to rely on Writer.com’s AI content detector? Switch to QuillBot for a similar free experience, or Originality.ai for more accurate paid detection.

Whatever tool you choose, remember: AI content detectors are instruments that support human judgment, not automated judges. Use them as one input in your evaluation process, not the final word.