Overview

GPTZero classifies writing as human, AI, or mixed, and flags suspected AI use at document, sentence, and word level. It accepts pasted text and DOCX, PDF, and image files, with batch scanning for up to 50 files at a time. Its stated language support includes English, German, Portuguese, French, and Spanish, and its detector covers text from ChatGPT, GPT-3 through GPT-6, Gemini, Claude, Copilot, and other models.

That breadth is useful when a reviewer handles varied writing and file types. The important limitation is that GPTZero says results can be wrong, perform better on longer English prose, and should not be used alone to punish students or make a final judgment. Its language range does not remove the need to consider the context and examine the writing itself.

Key features

The free detector returns confidence scores, AI vocabulary, explanations, and sentence-level highlights. Advanced Scan identifies the sections contributing most to an AI classification, while GPTZero 4o explains recurring writing patterns. These cues can focus a reviewer’s attention; they cannot establish authorship by themselves.

Writing Replay, plagiarism checking, writing feedback, and grammar checking extend the service into writing review. The Chrome extension scans web pages and Google Docs, where it can provide feedback in comments and writing-process reports. Google Classroom and Canvas integrations add assignment scan results and writing feedback, which makes GPTZero more relevant to educators already working in those systems than to someone seeking only a quick standalone check.

For developers, the API accepts text and files, supports batch inference, and returns detection probabilities at document, paragraph, and sentence level. It includes ready-to-use code in 17 programming languages and connects with Zapier. GPTZero says it does not store or collect documents submitted through API calls; dashboard inputs may be used in aggregate to improve the service. It also states that it is SOC 2 Type II compliant and describes encryption, vulnerability scans, penetration testing, and MFA access controls.

Pricing

GPTZero is freemium, with a free plan and a 14-day trial. The free plan is listed at 0.00 USD per free and includes 10,000 words per month, 50,000 characters, and free AI detection. A separate account allowance supports detection for texts up to 150,000 characters or batches of up to 250 files, while the technology page describes scanning up to 50 files at a time. For regular use, the stated 10,000-word monthly plan allowance is the more practical constraint to keep in view.

Essential costs 8.33 USD per month when billed annually and includes 150,000 words per month and 50,000 characters per scan. It suits individuals who need more monthly volume than the free plan allows, but not larger scans. Premium costs 12.99 USD per month when billed annually, raises the monthly allowance to 300,000 words, and keeps the 50,000-character scan cap; it is the stronger fit for frequent use of medium-length submissions.

Professional costs 24.99 USD per month when billed annually, with 500,000 words per month and a 150,000-character scan cap. That higher per-scan ceiling matters for users reviewing longer pieces as well as higher monthly volume. GPTZero says plan overages cost $0.00046 per word and permit use beyond the plan by up to 1 million words before an upgrade is required. The paid plans are presented with annual billing, so the monthly figures should not be read as month-to-month terms.

Platforms

GPTZero is available on the web, through a Chrome extension, and via API. The extension adds webpage and Google Docs scanning to browser workflows; the API fits teams building detection into their own tools. Google Classroom, Canvas, and Zapier integrations further suit education and automation use cases.

Who it's for

Educators can use the Classroom and Canvas integrations to review assignments alongside writing feedback, while editors, publishers, journalists, and hiring teams may find the layered highlights and explanations useful for directing closer review. Developers have an API with batch inference and multiple output levels. GPTZero is a poor fit for anyone who needs a detector to make a conclusive authorship or disciplinary decision: the service itself warns against that use.

Pros and cons

Pros: Classification at document, sentence, and word level, plus explanations and focused analysis, gives reviewers more to investigate than a single score.
Pros: Google Docs, Classroom, Canvas, API, and Zapier support make it adaptable to education and team workflows.
Pros: The API has batch inference and stated document non-retention, a useful combination for integration work handling submitted files.
Cons: Detection can be wrong and is stronger on longer English prose, limiting confidence across short or multilingual submissions.
Cons: Free use is capped at 10,000 words monthly, and the paid per-scan character ceilings remain 50,000 on Essential and Premium.
Cons: Annual billing applies to the published monthly paid-plan prices, and overage words incur a charge.

Alternatives

For a wider category comparison, browse AI Content Detectors, AI Content Detection Software, or Plagiarism Detection Software.

Originality.ai is another freemium option with web, extension, and API access; its free Basic plan limits users to three scans a day and 2,000 words per scan.
AI Detectors.io is a freemium option spanning web, macOS, Windows, extension, and API.
Pangram offers a free tier with 2,000 words per day, image scans, OCR, and support for over 20 languages.
Winston AI has a 14-day free trial with 2,000 credits and includes AI-content and image detection.
Copyleaks AI Detector combines AI detection and plagiarism detection, with support for 30+ AI-detection languages in its Personal plan.
It's AI has a free plan with 4,000 words, file upload, and three deep scans.
TrustOriginality.ai offers a web-only free tier limited to one text analysis per month.
Proofademic pairs multilingual AI detection with a plagiarism checker and report export on its free plan.

Verdict

GPTZero is a strong choice for educators and writing teams that want detection alongside document review, feedback, and integrations. Its layered explanations and workflow coverage are the main reasons to choose it; its imperfect detection, English-prose advantage, and warning against consequential decisions are the reasons to look elsewhere if you need a definitive authorship test.

	GPTZero	SlopTotal
Free plan	Yes	Yes
Free trial	Yes	No
Paid from	$8.33/mo	Free
Open source	No	No
Platforms	api, extension, Web	api, extension, Linux, macOS, self-hosted, Web, Windows
Free plan	Yes	Yes
API access	Yes	Yes
Browser extension	Yes	Yes
Batch scanning	Yes	Yes
Report exports	—	none

GPTZero vs SlopTotal

GPTZero

SlopTotal