Overview

GPTZero classifies writing as human, AI, or mixed, and highlights suspected AI use at document, sentence, and word level. It covers writing associated with ChatGPT, GPT-3 through GPT-6, Gemini, Claude, Copilot, and other models. It fully supports English, German, Portuguese, French, and Spanish; GPTZero says results can be wrong and perform better on longer English prose, so the language list should not be read as a promise of equal performance across languages.

Users can paste text or submit DOCX, PDF, and image files. Batch scanning supports up to 50 files at a time. A free account has a separate allowance of 10,000 words per month and 50,000 characters per scan, so the larger batch capacity does not mean unlimited monthly use.

Key features

The free detector returns confidence scores, AI vocabulary, explanations, and sentence-by-sentence highlighting. Advanced Scan identifies the sections contributing most to an AI classification, while GPTZero 4o explains recurring writing patterns. Those layers help a reviewer focus attention; none makes a probability score a definitive authorship finding.

Writing Replay, plagiarism checking, writing feedback, and grammar checking make GPTZero more useful to writing teams than a detector alone. Its Chrome extension scans webpages and Google Docs, adds citation checks and writing feedback in Google Docs comments, and provides writing-process reports. Google Classroom and Canvas integrations bring scan results and feedback into education workflows.

The API accepts text and files, returns probabilities at document, paragraph, and sentence level, and supports batch inference. Ready-to-use code covers 17 programming languages, and Zapier integration offers another way to connect workflows. GPTZero says API-submitted documents are not stored or collected; dashboard inputs may be used in aggregate to improve the service. It also states that it is SOC 2 Type II compliant and uses encryption, vulnerability scans, penetration testing, and MFA access controls.

Pricing

GPTZero uses a freemium model, with a free plan and a 14-day trial. The Free plan costs 0.00 USD per free and includes 10,000 words per month, 50,000 characters per scan, and AI detection. It is a sensible starting point for occasional checks, but its monthly word cap is modest for high-volume review.

Essential costs 8.33 USD per month when billed annually and includes 150,000 words per month and 50,000 characters per scan. Premium is 12.99 USD per month when billed annually, with 300,000 words per month and the same per-scan character cap. Professional costs 24.99 USD per month when billed annually, raising the allowance to 500,000 words per month and 150,000 characters per scan. The higher tiers suit heavier workloads; Professional is the one of these plans that raises the stated per-scan cap.

Overages cost $0.00046 per word, and users can exceed their plan by up to 1 million words before being asked to upgrade. That flexibility can prevent an immediate interruption, but it makes usage monitoring important. The published plan details give monthly word and scan-size limits, not seat counts.

Platforms

GPTZero runs on the web and through a Chrome extension, with API access for integrations and custom workflows. Google Classroom, Canvas, and Zapier support institutional and developer use. The extension and integrations make it a stronger fit for teams already working in those environments than for users seeking a standalone desktop application.

Who it's for

Educators can use classroom integrations and writing feedback to examine assignments, while publishing, journalism, and hiring teams can use document-level and sentence-level analysis as one input in authenticity reviews. Developers can build around the API’s file, text, and batch support. GPTZero is not appropriate as the sole basis for disciplinary decisions: it warns that no detector is fully accurate and says results should not be used as a final verdict or alone to punish students.

Pros and cons

Pros: Analysis ranges from document to word level, with explanations and sentence highlights that give reviewers more to investigate than a bare label.
Pros: Writing, plagiarism, and classroom tools make it useful beyond one-off AI checks, particularly for education and editorial workflows.
Pros: API batch inference, 17-language code examples, and integrations support teams that need to connect scanning to existing systems.
Cons: GPTZero says results can be wrong and work better on longer English prose, which limits how confidently a score can be used across short or multilingual writing.
Cons: The Free plan’s 10,000-word monthly allowance can be restrictive for frequent scanning, and paid overages accrue by the word.

Alternatives

For broader options, compare AI Content Detectors, AI Content Detection Software, and AI Detection Software; readers focused on similarity checks can also browse Plagiarism Detection Software.

ContentDetector.org is a free alternative across web, extension, iOS, macOS, and Windows, and also includes an AI text converter that accepts up to 1,000 characters.
Winston AI is another option with API, extension, and web access, plus a free plan and trial.
AI Detector Pro offers a free plan capped at three AI scans per month and charges separately for API use; it may suit readers who want its humanization allowance on a paid plan.
Pangram offers a free daily allowance of 2,000 words, image scans, OCR, support for over 20 languages, and browser and Google Docs integrations.
Proofademic combines multilingual detection with plagiarism checking and report export on its free plan, which includes a 1,000-word allowance and a three-day trial.
AI Detectors.io offers a free plan with 10,000 words per month, daily credits, and access across web, API, extension, macOS, and Windows.
Copyleaks AI Detector may be worth comparing for readers seeking AI and plagiarism detection with support for more than 30 AI-detection languages.
It's AI has a free plan with 4,000 words, file upload, three deep scans, and a Chrome extension.

Verdict

GPTZero is a strong choice for educators and writing teams that need detection alongside writing feedback, classroom integrations, or an API. Its detailed analysis and workflow reach are the main reasons to choose it; its fallibility and English-prose advantage are the reasons to keep human judgment central or look elsewhere for a tool whose stated coverage better fits a particular language or workload.

	GPTZero	Is It AI?
Free plan	Yes	No
Free trial	Yes	No
Paid from	$8.33/mo	—
Open source	No	No
Platforms	api, extension, Web	Web
Free plan	Yes	Yes
API access	Yes	—
Browser extension	Yes	—
Language coverage	—	english_only

GPTZero vs Is It AI?

GPTZero

Is It AI?