Direct answer
ZeroGPT is a free-first AI detector with paid Pro plans from $9 per month. It publishes a 98 percent accuracy figure on vendor test data. In practice ZeroGPT is a competent triage signal on raw AI text and drops on paraphrased or humanised text in the same patterns as every other detector in this class. The free tier is useful as a cross-check against GPTZero when you want a second opinion before escalating a flag. Not reliable enough to be used as proof.
ZeroGPT is one of the most-visited free AI detector sites, driven by a direct name match for a very high-volume query. This review covers what ZeroGPT measures, how its paid tier compares to the other mainstream detectors, and where the public evidence suggests the score should and should not be trusted. For the broader 7-detector landscape read best AI detectors in 2026.
What ZeroGPT measures
ZeroGPT returns a per-sentence highlight and an overall AI probability percentage. The underlying signal is the perplexity-and-burstiness class of classifier that every mainstream detector uses, with ZeroGPT's own training-data tuning. The per-sentence highlight is the main UX feature: you can see which specific sentences the detector flagged rather than guessing from an aggregate score.
Pricing at a glance
| Plan | Monthly price | Per scan limit | Features |
|---|---|---|---|
| Free | $0 | 15,000 characters | Basic scan + per-sentence highlights |
| Pro | From $9 | 50,000 characters | Batch upload, deep analysis |
| Business | From $18 | 150,000 characters | API access, team seats |
How we evaluated
We ran a batch of 25 passages through ZeroGPT's free scanner: 10 human-written passages from before 2022, 10 GPT-4-class drafts from 2026, and 5 of those drafts after a cadence-humaniser pass. We recorded the overall AI probability percentage and the per-sentence highlighting for each. The sample is small; it is enough for the qualitative findings below but not enough for an independent accuracy figure.
What we found
On raw GPT-4 passages ZeroGPT consistently returned AI probability above 90 percent and highlighted most sentences as AI-generated. On the pre-2022 human-written passages ZeroGPT returned below 25 percent AI probability in 9 of 10 cases. On humanised passages ZeroGPT scores dropped to roughly 40 to 60 percent AI probability, in the "uncertain" band where the tool is appropriately hedged.
ZeroGPT vs the other free detectors
The two most-used free AI detectors are ZeroGPT and GPTZero. Both read perplexity and burstiness; both return a probability score and per-sentence highlighting; both drop in reliability on paraphrased or non-native English text in the patterns documented by the Stanford HAI 2023 study (see AI detection and non-native English writers). Practically, the two tools often disagree by a dozen percentage points on the same borderline passage. The honest workflow for writers who want detection as a self-check is to run the passage through both and treat agreement as the stronger signal; the honest workflow for teachers or integrity officers is to treat either flag as the start of a conversation, not a verdict (see AI detectors for teachers).
When ZeroGPT is the right tool
- You are a writer self-checking a draft: the free 15,000-character scan is enough for most essays or sections, and the per-sentence highlights tell you which sentences to rewrite.
- You want a second opinion to GPTZero: running the same passage through two free detectors reduces single-detector false-positive risk.
- You accept the detector as a flag, not a verdict, in line with the AI detection explained guide and the best AI detectors 2026 landscape read.
Frequently asked questions
Is ZeroGPT more accurate than GPTZero?
On vendor-published figures both claim roughly similar accuracy. In independent evaluation the two tools fail in similar patterns on paraphrased and non-native English text. If you want to use detection as a signal rather than a verdict, run passages through both and treat agreement as the stronger flag.
Can ZeroGPT detect paraphrased AI text?
Less reliably. Paraphrasing changes the perplexity and burstiness signatures ZeroGPT reads; a sufficiently thorough paraphrase or a pass through a cadence humaniser drops the score meaningfully. For practical paraphrase and humanising moves see how to humanise ChatGPT text.
Is the free ZeroGPT scan good enough?
For most individual use cases, yes. The 15,000-character free scan covers typical essays and content pieces, and the per-sentence highlighting is included at the free tier.