Top 15 AI Text Detector Services (and Free): Research 2026

AI-generated text is now everywhere.

ChatGPT, Claude, Gemini, DeepSeek, Llama and other large language models are used to create articles, student papers, product descriptions, reviews, emails, SEO pages, research drafts and business documents.

These tools attempt to determine whether a piece of text was written by a human, generated by AI, or created through a combination of both.

But there is an important problem.

Almost every detector claims impressive accuracy, sometimes 95%, 99% or even 99.9%. Those figures are difficult to compare because companies test different datasets, different AI models and different definitions of “accuracy.”

So for this research, we did not simply collect vendor claims.

We checked the current websites, free plans, U.S. pricing and capabilities of 15 AI text detection services, and looked at recent independent research to answer the more important question:

Which AI detector is actually the most accurate?

How Do AI Text Detectors Work?

AI detectors are fundamentally different from plagiarism checkers.

A plagiarism checker searches for text that matches previously published material.

An AI detector usually does not know whether ChatGPT previously generated a particular paragraph.

Instead, it looks at statistical and linguistic patterns.

A language model predicts which token is likely to appear next.

That means machine-generated writing can exhibit statistical patterns different from spontaneous human writing.

Early AI detectors relied heavily on characteristics such as perplexity and burstiness.

Modern commercial detectors are more sophisticated. They typically use proprietary machine-learning classifiers trained on millions of examples of both AI and human writing.

That is also why detectors need constant updates.

A detector trained on GPT-3.5 may not perform equally well against GPT-5, Claude, Gemini, DeepSeek or future models.

How Accurate Are AI Detectors?

This is the hardest part of comparing them.

A vendor saying that its detector is “99% accurate” does not necessarily mean it will correctly identify 99 out of every 100 documents you upload.

Results depend heavily on:

• AI model;
• document length;
• language;
• writing genre;
• amount of human editing;
• use of paraphrasers;
• mixed human/AI content;
• detector threshold;
• age of the detection model.

False positives are especially important.

A tool that detects almost every AI document but incorrectly flags 5% of genuine human documents could be dangerous in education or recruiting.

The RAID benchmark was created partly to address this problem. It includes millions of texts across models, domains, generation strategies and adversarial modifications, demonstrating that detector performance can change dramatically depending on the testing conditions.

A newer peer-reviewed 2026 study provides particularly useful evidence.

Researchers tested Pangram, GPTZero, Copyleaks and Turnitin on 160 academic documents divided between human-written, fully AI-written, hybrid human/AI and humanized AI content.

Pangram produced the strongest results across the AI-containing categories and correctly handled the fully human documents in that dataset.

This is one reason we currently consider Pangram the detector with the strongest independent evidence in this comparison.

AI Detector Services Overview

Pangram

Goto Pangram

Pangram has become one of the most important competitors in AI detection because it combines a strong commercial product with unusually strong third-party testing results.

Free Plan

2,000 words per day.

The free version currently includes:

• text detection;
• three AI image scans per day;
• AI-assistance detection;
• interpretability features;
• document upload;
• OCR;
• browser extension;
• Google Docs integration;
• detection across 20+ languages.

Price

Individual: $20/month

Includes up to 300,000 words per month.

Professional: $65/month

Includes up to 1.5 million words, additional image scans and included API usage.

Developer API pricing is also available separately.

Why Pangram Is Interesting

Pangram’s strongest selling point is independent accuracy research rather than simply its own marketing.

A peer-reviewed 2026 academic study comparing Pangram, GPTZero, Copyleaks and Turnitin found Pangram performed best on fully AI-generated, hybrid and humanized documents.

For fully AI-generated papers, Pangram achieved 97.5% inclusive accuracy in the study, while competing systems substantially underestimated AI usage.

Earlier University of Chicago research also found Pangram maintained very low false-positive and false-negative rates across multiple genres and AI models.

Best for: accuracy-focused detection, publishers, education and organizations concerned about false positives.

 

Originality.ai

Goto Originality.ai

Originality.ai is built heavily around professional publishing rather than solely academic use.

It combines AI detection with plagiarism checking, readability analysis, website scanning and team workflows.

Free Plan

The current Basic plan is free and offers:

• three AI scans per day;
• maximum 2,000 words per scan;
• AI detection;
• DOC, DOCX and PDF uploads.

Price

Pro: $14.95/month

or $12.95/month when billed annually.

The plan includes 2,000 monthly credits, with one credit equal to 100 words for applicable scans.

Enterprise: $179/month

or an effective $136.58/month when billed annually.

Key Features

• AI detection;
• plagiarism detection;
• AI-paraphrasing detection;
• URL scanning;
• full-site scanning;
• readability analysis;
• team management;
• Chrome extension;
• scan history;
• API access on Enterprise.

Why Originality.ai Is Interesting

Originality.ai is particularly well suited to content businesses.

An SEO agency can scan articles, URLs or entire sites instead of manually checking isolated paragraphs.

Best for: publishers, SEO agencies, affiliate websites and editorial teams.

 

GPTZero

Goto GPTZero

GPTZero is one of the best-known AI detection products in the United States, particularly within education.

Free Plan

The free plan currently provides approximately:

10,000 words per month.

GPTZero confirms that its free plan can be used for AI detection and its Chrome extension.

Price

Current published pricing includes:

Essential: $14.99/month monthly or $8.33/month with annual billing.

Premium: $23.99/month monthly or $12.99/month annually.

Professional: $45.99/month monthly or $24.99/month annually.

Key Features

• AI detection;
• sentence-level analysis;
• plagiarism checking;
• batch upload;
• Chrome extension;
• Writing Replay;
• authorship analysis;
• integrations aimed at education;
• developer API;
• writing feedback.

Why GPTZero Is Interesting

GPTZero has expanded beyond the question:

“Does this final text look AI-generated?”

Its Writing Replay and authorship tools can also provide evidence about how a document was created.

That can be more useful than a single probability score.

GPTZero also publishes its own detailed benchmarks and raw predictions, although vendor-run benchmarks should still be distinguished from independent research.

Best for: teachers, universities and organizations interested in writing-process evidence.

 

Copyleaks

Goto Copyleaks

Copyleaks is one of the strongest enterprise-focused platforms in this comparison.

Free Access

The web detector can scan up to 25,000 characters without logging in, and new users receive limited free credits for additional testing.

Price

Personal: $16.99/month

or $13.99/month with annual billing.

Pro: $99.99/month

or $74.99/month annually.

Enterprise and education plans use custom pricing.

Key Features

• AI text detection;
• AI + plagiarism reports;
• 30+ AI detection languages;
• plagiarism detection in 100+ languages;
• AI image detection;
• batch scanning;
• website scanning on Pro;
• browser extension;
• Google Docs add-on;
• API;
• LMS integrations;
• enterprise analytics.

Why Copyleaks Is Interesting

Copyleaks is particularly attractive when detection needs to become part of an existing corporate or education system rather than remaining a website employees manually visit.

Best for: enterprises, universities, multilingual organizations and developers.

 

Winston AI

Goto Winston AI

Winston AI has expanded from text detection into a broader synthetic-content verification product.

Free Trial

2,000 credits for 14 days.

Price

Essential: $18/month or $10/month with annual billing.

Advanced: $29/month or $16/month annually.

Elite: $49/month or $26/month annually.

Key Features

• AI content detection;
• AI image detection;
• deepfake detection;
• OCR;
• document scanning;
• handwriting recognition;
• writing feedback;
• shareable PDF reports;
• teams;
• API.

Advanced and Elite tiers add broader plagiarism and team capabilities.

Why Winston AI Is Interesting

The unusual feature here is multimodal verification.

Winston can be relevant to publishers that need to inspect not only text but also images and other forms of synthetic content.

Best for: publishers, media organizations and content verification teams.

Turnitin

Goto Turnitin

Turnitin is fundamentally different from most other products in this list.

It is an institutional academic-integrity platform rather than a consumer AI checker.

Free Plan

No direct consumer free plan.

Price
Turnitin does not publish standardized individual pricing.

Licensing is generally purchased by schools, universities and other institutions.

Current AI Detection Requirements

As of September 2026, the AI Writing Report accepts documents containing:

• at least 300 words;
• up to 30,000 words;
• English;
• Spanish;
• Japanese;
• Arabic.

Supported files include DOCX, PDF, TXT and RTF.

Important 2026 Change

Turnitin changed its English AI report in August 2026.

Instead of separately highlighting AI-generated and AI-paraphrased material, the system now shows a unified AI-generated category.

Turnitin says this was intended to reduce overinterpretation of how the content was created.

It also does not display exact percentages between 1% and 19%, where false positives are more likely.

Why Turnitin Is Interesting

Turnitin’s advantage is not consumer pricing.

It is workflow.

Its AI detection sits inside an established academic-integrity environment with similarity checking, institutional policies, LMS integrations and authorship investigation.

Best for: universities, schools and institutional academic integrity.

 

Scribbr

Goto Scribbr

Scribbr has one of the easiest free detectors for students.

Free Plan

Unlimited free checks with up to 1,200 words per submission.

No signup is required.

Premium Price

Premium AI analysis is bundled with Scribbr’s plagiarism-checking product.

Pricing is per document rather than subscription:

Up to 7,499 words: $19.95

7,500–49,999 words: $29.95

50,000+ words: $39.95

Key Features

• free AI detection;
• AI-refined text identification;
• paragraph-level results;
• plagiarism checking on premium;
• document upload;
• no recurring subscription required.

Why Scribbr Is Interesting

The combination of free short checks and pay-per-document premium pricing makes Scribbr convenient for users who only need occasional academic checks.

Best for: students, researchers and occasional users.

 

QuillBot AI Detector

Goto QuillBot

QuillBot is primarily known for paraphrasing, but AI detection has become a significant part of its writing suite.

Free Plan

AI detection is available free.

There is a slight inconsistency in QuillBot’s own documentation.

Its June 2026 help documentation says AI detection itself is free and that Premium mainly changes batch-file capabilities.

Its current pricing page describes free AI Detector access as limited and Premium as full access.

Therefore, the safest description is:

Free detector available, with usage limits that may vary by platform.

Price

Free: $0

Premium: $19.95/month

or $8.33/month when billed annually ($99.95/year).

Key Features

• AI Detector;
• paraphrasing;
• plagiarism checking on Premium;
• grammar checking;
• AI Humanizer;
• summarizer;
• translation;
• browser extensions;
• batch AI detection on Premium.

Why QuillBot Is Interesting

It makes the most sense for someone who already wants an entire writing toolbox.

AI detection is one component rather than the whole product.

Best for: students, writers and existing QuillBot users.

Sapling AI Detector

Goto Sapling

Sapling is particularly interesting for developers.

Free Plan

2,000 characters per AI detector check.

Price

Pro: $25/month

or approximately $12/month with annual billing.

Enterprise starts at 10 seats with pricing beginning around $15 per seat per month.

API

Sapling’s AI Detector API starts at approximately:

$0.005 per 1,000 characters.

New API keys also receive a free quota of 50,000 characters per day and 250,000 characters per month.

Key Features

• AI probability;
• sentence-level scores;
• token probabilities through API;
• batch scanning;
• Google Docs;
• Chrome;
• Outlook;
• Word;
• developer API.

The current detector API is documented as English-only.

Why Sapling Is Interesting

Its API is unusually accessible compared with enterprise-focused competitors.

Best for: developers, SaaS products and automated content workflows.

 

Grammarly AI Detector

Goto Grammarly AI Detector

Grammarly is a particularly important addition to this comparison because it now offers a standalone free AI detector.

Free Detector

Users can paste text or upload a document and receive an estimate of what percentage appears AI-generated.

The standalone web detector is free.

Price

The broader Grammarly Free plan costs $0.

Grammarly Pro costs:

$30/month

or $144/year, equivalent to $12/month.

Pro includes AI detection and plagiarism checking within the Grammarly workflow.

Key Features

• free web AI detector;
• percentage score;
• plagiarism detection on paid plans;
• AI Detector agent;
• writing assistance;
• citations;
• Authorship;
• AI-assisted rewriting.

Accuracy

Grammarly currently says its detector ranks #1 on the RAID benchmark.

That is notable, but benchmark results should not automatically be generalized to every use case.

The independent 2026 academic study that favored Pangram did not include Grammarly, meaning there is currently no single head-to-head study covering every detector in this article.

Best for: users who already use Grammarly and want AI detection integrated into editing.

Isgen

Goto Isgen

Isgen is a newer detector with particularly broad multilingual positioning.

Free Plan

The current free detector allows approximately:

5,000 characters per scan.

It can be used without initially signing up.

Price

Academic: from $8/month when billed annually

Includes:

• 350,000 detection words per month;
• premium plagiarism checker;
• phrase-level analysis;
• batch uploads.

Ultimate: $24/month when billed annually

Includes unlimited detection words plus additional writing tools.

Key Features

• AI detection;
• human / mixed / AI classification;
• sentence analysis;
• phrase-level analysis;
• 80+ languages;
• plagiarism checking;
• AI image detection;
• bulk scanning;
• shareable reports.

Isgen’s current product page advertises support for more than 80 languages.

Why Isgen Is Interesting

Multilingual detection is its main differentiator.

Most detectors still focus primarily on English.

Best for: multilingual users, international education and content teams.

Undetectable AI Detector

Goto Undetectable AI

Undetectable AI is best known for AI humanization, but it also provides a standalone free detector.

Free Detector

The current detector:

• requires no signup;
• accepts up to 10,000 words on the detector page;
• supports major models including ChatGPT, Claude, Gemini and DeepSeek;
• supports multiple languages.

The company says the detector itself is free.

Paid Plans

Paid plans primarily expand the humanization and writing tools.

Pricing currently starts at:

$9.99/month for 10,000 words

or approximately $5/month with annual billing.

Why Undetectable AI Is Interesting

Users can run a quick AI check without registering or purchasing a detector subscription.

However, its business model is unusual because the same company also sells software designed to rewrite AI-generated text.

Best for: fast free checks and users wanting detection alongside rewriting tools.

Surfer AI Detector

Goto Surfer AI Detector

Surfer is primarily an SEO platform, but it offers a free standalone AI content detector.

Free Detector

Surfer currently offers a web-based AI detector that can identify and highlight likely AI-generated writing.

Its detector currently focuses on English.

Price

The detector itself can be used free.

The broader Surfer platform currently starts with:

Discovery: $49/month when billed annually.

Higher plans expand Surfer’s SEO optimization, AI visibility, content and humanization capabilities.

Key Features

• free AI detection;
• AI probability;
• AI highlighting;
• AI Humanizer integration;
• SEO content workflow;
• plagiarism features inside paid Surfer plans.

Why Surfer Is Interesting

Surfer makes more sense for marketers than educators.

An SEO professional can move between content optimization, AI detection and humanization within one ecosystem.

Best for: SEO specialists, agencies and content marketers.

 

SmallSEOTools AI Content Detector

Goto SmallSEOTools AI Detector

SmallSEOTools offers one of the lowest-friction free options in this comparison.

Free Plan

The current tool supports up to approximately:

2,000 words per check.

No registration is required.

Price
The AI detector itself does not require a paid subscription.

Key Features

• AI percentage;
• human-content percentage;
• document upload;
• multilingual detection;
• no signup;
• repeated free use.

Accuracy

SmallSEOTools advertises 99.9% accuracy.

We would treat that as a vendor claim rather than an independently verified figure, since we found much stronger independent academic evidence for products such as Pangram.

Why SmallSEOTools Is Interesting

It is extremely easy to access.

There is no account setup, credit card or subscription decision before running a scan.

Best for: quick free checks and occasional users.

 

ContentDetector.AI

Goto ContentDetector.AI

ContentDetector.AI is another completely accessible web-based detector.

Free Plan

The service describes its detector as free with no stated usage limit.

For better accuracy, it recommends entering at least approximately 250 words.

The detector currently operates in English only.

Key Features

• AI probability score;
• ChatGPT detection;
• Gemini detection;
• Claude detection;
• word count;
• character count;
• simple browser interface.

Why ContentDetector.AI Is Interesting

It is one of the simplest products here.

There is no complex dashboard, institutional deployment or enterprise sales process.

Paste the text and receive a probability.

Best for: completely free basic AI checks.

 

AI Detector Price and Feature Comparison

AI Detector	Free Access	Starting Paid Price	Plagiarism	API / Enterprise	Best Use Case
Pangram	2,000 words/day	$20/mo	Yes	Yes	Accuracy-focused detection
Originality.ai	3 scans/day, 2,000 words each	$14.95/mo	Yes	Yes	SEO & publishing
GPTZero	10,000 words/mo	$14.99/mo	Yes	Yes	Education
Copyleaks	Free web scan / credits	$16.99/mo	Yes	Yes	Enterprise & multilingual
Winston AI	2,000-credit trial	$18/mo	Paid tiers	Yes	Text + image verification
Turnitin	No consumer plan	Custom	Yes	Institutional	Universities
Scribbr	Unlimited 1,200-word checks	$19.95/document	Yes	Limited	Students
QuillBot	Yes, limited	$19.95/mo or $8.33 annual equivalent	Premium	Team	Writing suite
Sapling	2,000 chars/check	$25/mo	No core focus	Yes	Developers
Grammarly	Free web detector	Pro $30/mo or $12 annual equivalent	Pro	Enterprise	Writing workflow
Isgen	5,000 chars/check	$8/mo annual equivalent	Yes	Yes	Multilingual detection
Undetectable AI	Free detector	$9.99/mo	Additional tools	Yes	Quick free checks
Surfer	Free detector	Platform from $49/mo annual	Paid ecosystem	Business	SEO & marketing
SmallSEOTools	Free, ~2,000 words/check	Not required	Separate tool	Limited	Casual free checks
ContentDetector.AI	Free	Not required	Basic	No major enterprise focus	Simple free detection

Prices are in U.S. dollars and were checked against available U.S. product and pricing pages on September 23, 2026. Subscription prices, promotions and limits can change.

What Are the Best Free AI Detectors?

If you do not want to pay, there are now surprisingly good options.

Pangram

2,000 words every day is enough for regular individual use, and it gives users access to the same general ecosystem as Pangram’s commercial product.

GPTZero

10,000 words per month makes GPTZero practical for students and educators who only need occasional scans.

Copyleaks

The ability to run a relatively large browser scan without first purchasing a subscription makes it useful for quick checks.

Scribbr

Unlimited 1,200-word checks are particularly useful when reviewing essays section by section.

Grammarly

The standalone web detector is convenient if you already use Grammarly.

QuillBot

Free AI detection is useful for existing QuillBot users, although the current product page indicates limits can apply to free access.

Isgen

A 5,000-character free scan plus multilingual analysis makes Isgen worth testing for non-English content.

Undetectable AI

The free no-signup detector is one of the easiest ways to perform a fast check.

Surfer

Useful for marketers and SEO specialists who want a detector connected to an SEO-oriented ecosystem.

SmallSEOTools and ContentDetector.AI

Both offer very low-friction free checking without requiring a professional subscription.

Our Conclusion

Most convincing independent evidence for long-form and academic AI detection: Pangram.

Most interesting alternative for education and authorship evidence: GPTZero.

Strongest publisher/SEO workflow: Originality.ai.

Strong enterprise and multilingual stack: Copyleaks.

Most deeply integrated institutional academic product: Turnitin.

For users who only want a quick free check, Pangram, GPTZero, Scribbr, Grammarly, QuillBot, Isgen and several completely free web detectors make it unnecessary to buy a subscription immediately.

Can AI Detectors Be Trusted?