GPTZero vs Noplag
GPTZero
gptzero.me
Noplag
noplag.comSide by side
| Figure | GPTZero | Noplag |
|---|---|---|
| Price from | $8.33/mo | $9.99/mo |
| Free plan | Yes | Yes |
| Free trial | Yes | Yes |
| Open source | — | Yes |
| Web | Yes | Yes |
| Windows | — | Yes |
| macOS | — | Yes |
| Linux | — | Yes |
| API | Yes | Yes |
| Self-hosted | — | Yes |
| Plans published | 4 | 4 |
| Spec score · Plagiarism Detection Software | 9.1 (#3) | 9.1 (#4) |
| API | The API accepts files and text and returns AI-detection probabilities at document, paragraph, and sentence level, including batch inference. | The developer API is REST with an OpenAPI spec and webhooks, and is available on paid tiers. |
| Founded | 2023 | 2014 |
| Headquarters | New York, United States | San Francisco, United States |
| Integrations | GPTZero lists Google Classroom and Canvas LMS integrations, an API for developers, and a Zapier integration. | The features page lists Canvas, Moodle, Blackboard, and Brightspace integrations via LTI 1.3. |
| Languages | GPTZero says it fully supports English, German, Portuguese, French, and Spanish. | Detection is calibrated at launch for English, Spanish, Portuguese, Polish, and Ukrainian. |
| Privacy | 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. | Noplag states that submitted documents are not used to train models or shared between accounts, and EU data residency is available. |
| Security | GPTZero states it is SOC 2 Type II compliant and lists CCPA, GDPR, FERPA, HECVAT, and VPAT commitments or assessments. | Noplag says it encrypts data in transit and at rest and does not yet hold formal attestations such as SOC 2. |
| Support | The site directs users to its Support Center and customer service team for help. | Free includes community Discord support, Pro includes email support, and Premium includes priority support with a 12-hour response target. |
| What it does | GPTZero detects likely AI-generated writing and identifies AI use at document, sentence, and word level. | Noplag checks submitted text or files for plagiarism and returns similarity scores, highlighted overlaps and source links. |
Plans
GPTZero
- FreeFree
- Essential$8.33 a month
- Premium$12.99 a month
- Professional$24.99 a month
In their own words
GPTZero
GPTZero identifies likely AI-generated writing and highlights detected AI use at document, sentence, and word level. Its detector can classify text as human, AI, or mixed, and provides confidence scores, explanations, AI vocabulary, and sentence-by-sentence highlighting. Advanced Scan points to passages contributing most to an AI classification. Users can submit pasted text or DOCX, PDF, and image files; the technology page says it can analyze up to 50 files at a time. GPTZero lists support for English, German, Portuguese, French, and Spanish, and detector coverage for text from ChatGPT, GPT-3 through GPT-6, Gemini, Claude, Copilot, and other models. Additional tools include Writing Replay, plagiarism checking, writing feedback, and grammar checking. The Chrome extension scans webpages and Google Docs, and integrations include Google Classroom, Canvas, an API, and Zapier. GPTZero says its results may be wrong, perform better on longer English prose, and should not be used alone to punish students. The free plan costs nothing. Paid plans start at $8.33 a month when billed annually.
Noplag
Noplag is an open-source plagiarism checker with a hosted cloud service and an engine released under Apache 2.0. Its current matching uses winnowing fingerprints and live-web comparison to find verbatim and near-verbatim copying; it does not detect paraphrase. Sources include the open web, Common Crawl, Wikipedia, academic indexes, the Noplag Database and users’ own folders. Submit DOCX, PDF, TXT, ODT or RTF files, paste text or provide a URL. Reports link matches to their sources, display similarity scores and exact overlapping text, and can be exported as PDFs. Detection is calibrated at launch for English, Spanish, Portuguese, Polish and Ukrainian. AI-content detection is marked as coming soon and intended as a separate signal. The free plan allows three checks per month, up to 2,500 words per check, with community Discord support. Pro costs $9.99 a month and includes 50 monthly checks, up to 25,000 words per check, database and academic-index matching, REST API and webhooks, and email support. A 14-day trial is listed.