GPTZero vs ZeroGPT: similar names, very different track records
GPTZero vs ZeroGPT is an easy mix-up: the names are almost mirror images, but the tools come from different companies. GPTZero has far more independent testing behind it. ZeroGPT lets you paste more text without an account and says it does not save what you check.
Our verdict: for anything that matters, GPTZero is the safer of the two. It appears on the public RAID leaderboard and in recent university studies, while the main independent test of ZeroGPT we found, a 2024 preprint, saw it wrongly flag about one human essay in four. ZeroGPT is fine for a quick, account-free look at a longer passage. Neither should settle a grade or a hiring decision on its own.
GPTZero vs ZeroGPT at a glance
Limits and prices as listed on each site at the time of writing (October 2026). IsThisAiWritten, our own free detector, is in the first column for comparison.
| IsThisAiWritten | GPTZero | ZeroGPT | |
|---|---|---|---|
| Check without an account | Any length | Up to 10,000 characters | Up to 15,000 characters |
| Free account | Not needed | 10,000 words a month | 15,000 characters per check |
| Paid limit per check | No limit, free | 50,000 or 150,000 characters | 100,000 to 350,000 characters |
| Entry paid plan | Free | $23.99 a month, or $12.99 a month yearly | 12.99 a month, or 7.99 a month yearly (shown to us in Swiss francs) |
| Keeps your text | Never uploaded; checked in your browser | Dashboard inputs stored and used in aggregate | Says text is not saved or used for training |
How the two compare on outside testing and features:
| GPTZero | ZeroGPT | |
|---|---|---|
| Independent test results | RAID leaderboard and several 2025 to 2026 studies | Older studies only (2023 and 2024) |
| Sentence highlighting | Yes | Yes |
| Languages | Five fully supported | Claims all languages |
| Classroom tools | Writing Replay, Canvas, Google Classroom | No LMS integration listed |
What independent testing says about GPTZero vs ZeroGPT
There is no recent study that puts these two head to head. What exists is uneven: GPTZero shows up in current research, ZeroGPT mostly in older work. Keep the dates in mind, because both products have changed.
RAID benchmark
RAID is a public benchmark for AI text detectors presented at ACL 2024. Each team runs its own detector on a shared test set, and the maintainers score the predictions. GPTZero's entry catches 95.7% of AI texts when its threshold is set so that only 1% of human texts are flagged. With adversarial tricks such as paraphrasing and homoglyphs included, that drops to 92.9%. ZeroGPT has no entry on the leaderboard, so there is nothing to compare.
University studies of GPTZero, 2025 and 2026
A University of Chicago working paper (Jabarian and Imas, 2025) found GPTZero's false positive rate low and steady, at about 0.7%, though it missed around half or more of AI passages once a humanizer tool had rewritten them. A University of Maryland study the same year had similar results: few false positives, weaker on humanized text. A 2026 study from Vrije Universiteit Brussel found GPTZero underestimated AI content in academic papers. None of these tested ZeroGPT.
The 2024 DUPE preprint
Two Virginia Tech researchers, James Weichert and Chinecherem Dimobi, ran 212 University of Michigan student essays written between 2004 and 2009 through ZeroGPT, along with ChatGPT essays on the same titles. ZeroGPT wrongly flagged 24.64% of the human essays and missed 19.14% of the AI ones. The authors wrote that its overall accuracy, 78.62%, did not match the "up to 98%" on ZeroGPT's site. GPTZero, tested on a smaller set of 80 essays, flagged none of the human essays and missed 2.5% of the AI ones. This is a preprint, not peer-reviewed, and it predates the current versions of both tools.
The 2023 Stanford study on non-native writers
Weixin Liang, James Zou and colleagues at Stanford tested seven detectors, GPTZero and ZeroGPT among them, on 91 TOEFL essays written by non-native English speakers. On average across the seven, 61.22% of those human essays were labelled AI-generated. Both tools have changed since then. GPTZero now says it retrains its model to keep false positives on English learners' writing at 1%; we found no matching statement from ZeroGPT.
What each company claims
ZeroGPT's homepage advertises 98.4% detection accuracy, a false positive rate under 1% and coverage of more than 35 model families. Its FAQ is more cautious, describing accuracy "up to 98%" and an aim to get the error rate below 2%. GPTZero's homepage claims 99% accuracy. These are the vendors' own figures, not independent results.
Free limits and prices
For a single check without an account, ZeroGPT takes more: 15,000 characters against GPTZero's 10,000. That is roughly 2,500 words against 1,700, depending on the text. A free GPTZero account adds a monthly allowance of 10,000 words and one Advanced Scan.
GPTZero Premium costs $23.99 a month, or $12.99 a month on a yearly plan, for 300,000 words and up to 50,000 characters per scan. Professional is $45.99 ($24.99 yearly) for 500,000 words and 150,000 characters per scan. ZeroGPT's personal plans run from Pro to Max, with per-check limits between 100,000 and 150,000 characters; its Expert plan goes to 350,000. When we checked, Pro was listed at 12.99 a month or 7.99 a month billed yearly, in Swiss francs. The currency you see depends on where you are.
Privacy and data
ZeroGPT's FAQ says that when you check text "your text will not be saved, shared or be available online", and that it will not be used to train its detector. GPTZero's FAQ says it stores inputs made through its dashboard and uses that data in aggregate to improve the service; text sent through its API is not stored. GPTZero says it is SOC 2 Type II compliant and supports deletion requests. If a document is confidential, read both policies before pasting.
Features beyond the score
ZeroGPT is a broad writing suite. Next to the detector it offers a paraphraser, summarizer, grammar checker, translator, a chatbot and an AI humanizer, plus PDF reports, batch file uploads and bots for WhatsApp and Telegram. GPTZero is more focused on schools and publishers: Writing Replay shows how a Google Doc was typed, and there is a Chrome extension plus Canvas and Google Classroom integrations. GPTZero has been part of Superhuman, the company formerly known as Grammarly, since a deal announced in June 2026.
Which should you use?
Teachers, editors and anyone making a decision about a person should lean toward GPTZero, or toward a tool with even stronger independent results, and should still talk to the writer before acting. ZeroGPT works as a quick look at a longer passage when you don't want an account and the stakes are low.
A free option for longer text: IsThisAiWritten
If 10,000 or 15,000 characters is too short, IsThisAiWritten takes English text of any length with no account and checks it locally in your browser, so nothing is uploaded. Every word is scanned, never sampled, and the report shows a sentence map and an AI-likeness score rather than a single number. Like any detector, it can be wrong in both directions, so treat a result as a reason to look closer, not as proof. The methodology page explains how it is tested.
Where GPTZero and ZeroGPT are better than us: both work in more than one language, while we are English only. GPTZero has Writing Replay, a Chrome extension and Canvas and Google Classroom integrations. ZeroGPT bundles a paraphraser, grammar checker and translator, and offers PDF reports and batch file uploads. If you need any of those, use one of them; if you want privacy and no length limit, start with ours.
Sources
- RAID benchmark leaderboard, checked October 2026
- RAID repository and submission rules, checked October 2026
- Weichert and Dimobi, DUPE: Detection Undermining via Prompt Engineering for Deepfake Text (arXiv, 2024), checked October 2026
- Liang et al., GPT detectors are biased against non-native English writers (2023), checked October 2026
- Jabarian and Imas, Artificial Writing and Automated Detection (BFI Working Paper 2025-116), checked October 2026
- Russell, Karpinska and Iyyer, University of Maryland detector study (2025), checked October 2026
- Van Vlasselaer et al., Who wrote this? (International Journal for Educational Integrity, 2026), checked October 2026
- ZeroGPT homepage and FAQ, checked October 2026
- ZeroGPT pricing, checked October 2026
- GPTZero homepage, checked October 2026
- GPTZero pricing, checked October 2026
- GPTZero FAQ, checked October 2026
- GPTZero privacy and security, checked October 2026
- GPTZero: accuracy statistics, checked October 2026
- BetaKit: Superhuman, formerly Grammarly, acquires AI detector GPTZero, checked October 2026
Questions
Are GPTZero and ZeroGPT the same company?
No. They are separate products from separate companies that happen to have near-identical names. GPTZero was founded by Edward Tian and Alex Cui and was bought by Superhuman (formerly Grammarly) in 2026. ZeroGPT is a separate service at zerogpt.com.
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