Overview

GPTZero classifies writing as human, AI, or mixed and highlights likely AI use at document, sentence, and word level. It covers text from ChatGPT, GPT-3 through GPT-6, Gemini, Claude, Copilot, and other models. Users can paste text or submit DOCX, PDF, and image files; batch analysis can process up to 50 files at a time. That makes it practical for recurring review, though the detector’s range does not remove the need to assess each result in context.

It fully supports English, German, Portuguese, French, and Spanish. GPTZero says performance is better on longer English prose and that results can be wrong. Those caveats matter for short submissions and multilingual review: a score should not be treated as a final verdict or used alone to punish a student.

Key features

The free detector supplies confidence scores, AI vocabulary, explanations, and sentence-level highlighting. Advanced Scan points to the sections contributing most to an AI classification, while GPTZero 4o explains recurring writing patterns. These cues help a reviewer decide what to examine next, but they cannot establish authorship by themselves.

Writing Replay, plagiarism checking, writing feedback, and grammar checking broaden the product beyond detection. The Chrome extension scans webpages and Google Docs, adds feedback in Docs comments, and provides writing-process reports. This is a stronger fit for educators and editors working inside familiar documents than for someone who only needs an occasional standalone scan.

Google Classroom and Canvas integrations provide assignment scan results and writing feedback. Developers can use an API that accepts text and files, returns probabilities at document, paragraph, and sentence level, and supports batch inference; ready-to-use code is available in 17 programming languages. Zapier integration also supports connected workflows. These options make GPTZero more adaptable for institutions and products, though the API’s document-handling terms differ from dashboard use: GPTZero says API submissions are not stored or collected, while dashboard inputs may be used in aggregate to improve the service.

GPTZero says it is SOC 2 Type II compliant and describes encryption, regular vulnerability scans, penetration testing, and MFA access controls. Those safeguards are relevant for organizations reviewing sensitive work, but they do not change the need to consider the stated dashboard data use.

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. A separate free-account allowance is described as texts up to 150,000 characters or batches of up to 250 files; users should distinguish those account limits from the plan’s stated monthly word quota.

Essential costs 8.33 USD per month when billed annually and includes 150,000 words per month with 50,000 characters per scan. It suits regular individual review when the free monthly allowance is too small. Premium is 12.99 USD per month when billed annually, raising the monthly quota to 300,000 words while retaining the same 50,000-character scan cap; it is the more suitable step for heavier routine volume. Professional costs 24.99 USD per month when billed annually and includes 500,000 words per month with a 150,000-character scan cap, which better fits users handling larger documents and the highest stated volume among these plans.

GPTZero says overages cost $0.00046 per word, and users can exceed a plan by up to 1 million words before being asked to upgrade. That flexibility can prevent an unexpected spike from immediately blocking work, but high-volume users should account for the per-word charge. No seat counts are stated for these plans.

Platforms

GPTZero is available on the web, through an extension, and by API. The browser extension, classroom integrations, and developer options make it more useful across institutional and technical workflows than a web-only checker. The API is the clearest fit for automated review; individual users can use the web detector without adopting those integrations.

Who it's for

Educators can use assignment scans and writing feedback in Google Classroom or Canvas, while publishers, journalists, and hiring teams can use document and sentence-level analysis as one input when assessing writing authenticity. Developers have an API for embedding detection and batch processing. GPTZero is a poor fit for anyone seeking a definitive authorship judgment: the company itself warns that detectors are fallible and should not be used alone to punish students.

Pros and cons

Pros: Detection includes confidence scores, explanations, and fine-grained highlighting, giving reviewers more context than a single classification.
Pros: Writing feedback, Replay, plagiarism and grammar checks, plus classroom and developer integrations support workflows beyond one-off scanning.
Pros: The free plan provides ongoing detection, and paid plans scale from 150,000 to 500,000 words per month.
Cons: Results can be wrong and are stronger on longer English prose, limiting their value as a standalone basis for consequential decisions.
Cons: The free plan’s 10,000-word monthly quota is modest for sustained review, while overages carry a per-word charge.
Cons: Dashboard inputs may be used in aggregate to improve the service, unlike API documents, which GPTZero says it does not store or collect.

Alternatives

AI Detector Pro is another freemium web option; its free plan offers three AI scans per month, while its Basic plan includes 103 monthly scans and unlimited humanizations. Pangram is worth considering for a free daily allowance of 2,000 words, image detection, OCR file upload, and a browser extension with Google Docs integration.

Proofademic pairs multilingual AI detection with plagiarism checking and report export on its free plan, which includes 1,000 words and a three-day trial. Winston AI may suit readers who want to try a 14-day plan with 2,000 credits, AI content and image detection, document and OCR scanning, and email and chat support.

ContentDetector.org is a free alternative with web, browser extension, desktop, and iOS platforms. Copyleaks AI Detector is an alternative for readers seeking AI and plagiarism detection, with a Personal plan that includes 30+ detection languages and up to 300,000 words per billing period.

AI Detectors.io offers a forever-free plan with 10,000 words per month and one free credit daily, but limits use to 500 words per use. Detecting-AI.com is another freemium option, with up to 300 detections per day and a 15,000-character check limit on its free plan.

For broader comparison, browse AI Content Detectors, AI Content Detection Software, AI Detection Software, and Plagiarism Detection Software.

Verdict

GPTZero is the strongest fit for educators and writing teams that need detection alongside document feedback, classroom connections, and scalable review tools. Its practical advantage is the combination of granular explanations and workflow integrations; its central limitation is that detector output can be wrong and should never carry a consequential decision on its own. Choose it to guide human review, not to replace it.

	GPTZero	JPlag
Free plan	Yes	Yes
Free trial	Yes	No
Paid from	$8.33/mo	Free
Open source	No	No
Platforms	api, extension, Web	api, Linux, macOS, self-hosted, Windows
Free plan	Yes	Yes
API access	Yes	Yes
Browser extension	Yes	No
AI detection	—	No
LMS integrations	—	No

GPTZero vs JPlag

GPTZero

JPlag