Overview

The service classifies writing as human, AI, or mixed and marks suspected AI use at document, sentence, and word level. It supports text associated with ChatGPT, GPT-3 through GPT-6, Gemini, Claude, Copilot, and other models. Users can paste text or submit DOCX, PDF, and image files, with batch analysis of up to 50 files at a time.

GPTZero fully supports English, German, Portuguese, French, and Spanish, but says detection performs better on longer English prose and can be wrong. Its labels and explanations are useful prompts for further review, not proof of who wrote a text. The company advises against using results as a final verdict or alone to punish a student.

Key features

The free detector returns confidence scores, AI vocabulary, explanations, and sentence-by-sentence highlighting. Advanced Scan shows which sections most contribute to an AI classification, while GPTZero 4o explains recurring writing patterns. That added context can help a reviewer focus attention, though it does not remove the need to assess the writing independently.

Writing Replay, plagiarism checking, writing feedback, and grammar checking make GPTZero more useful to people who want a broader writing workflow than detection alone. The Chrome extension scans webpages and Google Docs; in Docs it can provide feedback in comments and writing-process reports. Google Classroom and Canvas integrations bring assignment scan results and writing feedback into education workflows.

Developers can use an API that accepts text and files and returns detection probabilities at document, paragraph, and sentence level, including batch inference. 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, while dashboard inputs may be used in aggregate to improve the service. It also says 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 costs 0.00 USD per free and includes 10,000 words per month, 50,000 characters, and free AI detection. Elsewhere, GPTZero describes free-account detection for texts up to 150,000 characters or batches of up to 250 files; those thresholds differ from the plan’s stated monthly word allowance, so frequent users should keep the monthly cap in view.

Plan	Price	Included allowance	Best fit
Free	0.00 USD per free	10,000 words/month; 50,000 characters	Occasional scans or trying the detector
Essential	8.33 USD per month, billed when paying annual	150,000 words/month; 50,000 characters per scan	Regular individual use beyond the free allowance
Premium	12.99 USD per month, billed when paying annual	300,000 words/month; 50,000 characters per scan	Higher monthly volume without a larger per-scan limit
Professional	24.99 USD per month, billed when paying annual	500,000 words/month; 150,000 characters per scan	Heavier workloads or longer individual scans

The paid plan prices are monthly rates when billed annually. Overages cost $0.00046 per word, and users can exceed a plan by up to 1 million words before being asked to upgrade. The free tier is a sensible starting point, but its monthly word allowance is modest for teams scanning routinely. Premium raises monthly volume but not the per-scan character ceiling; Professional is the option for longer scans. No seat allowances are stated, so teams should confirm fit before choosing a plan.

Platforms

GPTZero is available on the web, through a Chrome extension, and by API. Classroom integrations support Google Classroom and Canvas, while Zapier offers another route to connect workflows. The extension and integrations make it more practical for recurring review than a standalone checker, particularly for educators and teams already working in those tools.

Who it's for

Educators can use GPTZero to examine assignments and give writing feedback, but should pair any flag with other evidence rather than make a disciplinary decision from a score. Editors, publishers, journalists, and hiring teams may find its sentence-level explanations and writing tools useful when checking authenticity. Developers can use the API for batch review and finer-grained probabilities; those handling sensitive documents may prefer API submissions over dashboard inputs, given GPTZero's stated data-handling distinction.

Pros and cons

Pro: Sentence-level highlighting, explanations, and Advanced Scan give reviewers more useful context than a bare AI/human label.
Pro: Google Docs, Classroom, and Canvas integrations fit established writing and assignment workflows.
Pro: API batch inference and code in 17 programming languages support developer use.
Con: GPTZero says results can be wrong and favors longer English prose, limiting confidence across languages and short texts.
Con: The free plan's 10,000-word monthly allowance may be quickly exhausted by regular classroom or editorial scanning.
Con: Dashboard inputs may be used in aggregate to improve the service, unlike documents submitted through API calls, which GPTZero says it does not store or collect.

Alternatives

For a broader comparison, browse AI Content Detectors, AI Detection Software, and AI Content Detection Software. Readers focused on plagiarism tools can also consult Plagiarism Detection Software.

Originality.ai is worth considering if its free AI-detection tier, capped at three scans per day and 2,000 words per scan, matches a lighter workload. Pangram may suit users who want a stated 2,000 words per day, image detection scans, OCR, and support for over 20 languages. For a free plagiarism-oriented option, Plagium offers five daily searches with a 4,000-character limit and no API access on its free account. Copyscape, Noplag, Noplag Engine, Quetext AI Detector, and SmallSEOTools Plagiarism Checker are other options to compare.

Verdict

GPTZero is a strong fit for educators and writing teams who need layered AI analysis plus feedback and integrations in their existing workflows. Its broad file and API support adds flexibility, but the detector’s acknowledged errors and weaker performance outside longer English prose make it unsuitable as a standalone authority. Choose it to guide human review; look elsewhere if you need certainty rather than an indicator.

	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