Two generations in, still one job:sounding human.
Ghost-2 is the second generation of Ghost, our proprietary humanization model. Like every Ghost model, it rewrites AI-generated text so it reads like it was written by a human, bypassing every major AI detector while preserving meaning, tone, and fluency.
It is now the default model behind every humanization on UndetectedGPT: the web app, the API, and Ghost Writer. Ghost-1 stays available for anyone who wants to keep their existing setup.
Built to beat detectors
Ghost-2 isn't a generic paraphraser. It was purpose-built to bypass GPTZero, Originality.ai, ZeroGPT, Turnitin, Quillbot, Grammarly, and more.
Preserves meaning and tone
Ghost-2 rewrites how something is said, not what is said, keeping your original meaning, structure, references, and citations.
Continuously improving
As detectors evolve, so does Ghost-2. We constantly evaluate and update the model to stay ahead.
Tested where it counts.
Every Ghost release runs the same eval: pass rate (scored <30% AI) across 100,000+ unique English texts, scored independently by six detectors.
Evaluated on deduplicated English-only texts, each scored by six independent detectors. "Pass" = detector returns <30% AI probability. *Turnitin tested on 500 inputs.
of 11 humanizers · September 2026
GPTZero · Originality.ai · Winston AI · ZeroGPT · Grammarly · QuillBot · Copyleaks
Ranked #1 of 11 humanizers in the September 2026 AI Humanizer Benchmark, scored across 7 detectors with a fixed public methodology.
See the leaderboardThe two sets of numbers measure different things: the benchmark uses inputs that are deliberately hard to humanize, while the pass rates above are measured on text typical of everyday use.
From Ghost-1 to Ghost-2.
Detectors change constantly, so a model frozen in time slowly goes stale. Every Ghost release re-runs the same benchmark, and the next model is already in the works while the current one ships.
- nextIn training
The next Ghost
Training never stops. The next generation is already in the works against the newest detector releases.
- v2.0Now
Ghost-2
Second-generation model, retrained end to end on a broader mix of writing styles and the newest detector versions. Mean pass rate 98.3% across six detectors, up from Ghost-1's 96.2%.
- v1.0Previous generation
Ghost-1
First stable release. Mean pass rate 96.2% across six detectors. Still available through the API and model settings.
- v0.9Last cycle
Tone preserve
Reduced semantic drift on long-form academic and technical text.
- v0.8Earlier
Turnitin push
Added Turnitin to the eval set; pass rate moved 91 → 97%.
- v0.7Earlier
Citation lock
References, footnotes, and inline citations are no longer rewritten.
How we evaluate.
The same eval runs every release. No per-detector tuning, no hand-picked samples.
- 01
Source
Sample 100,000+ AI-generated English texts spanning essays, technical docs, blog posts, and conversational prose.
- 02
Humanize
Each text is rewritten by Ghost-2 with default settings (no per-detector tuning or retries).
- 03
Detect
Outputs are scored independently by six detectors. We never see scores during humanization.
- 04
Score quality
Outputs are also scored by general-purpose LLMs to check that each rewrite preserves meaning, structure, and fluency.
- 05
Pass / fail
A text passes a detector if it returns less than 30% AI probability. Mean pass rate is averaged across detectors, not texts.
Ghost-2 at a glance.
The numbers behind the model. What it is, what it does, and where it runs.
- Model family
- Ghost
- Version
- 2.0
- Type
- Humanization (text-to-text)
- Languages
- EN primary · 100+ supported
- Eval set
- 100,000+ deduplicated EN texts
- Detectors covered
- 10+ (GPTZero, Originality.ai, ZeroGPT, Turnitin, Quillbot, Grammarly, and more)
- Mean pass rate
- 98.3%
- Released
- Live
- Previous version
- Ghost-1 · available via API and model settings
Live everywhere we ship.
Ghost-2 is the default for every UndetectedGPT user, in every surface. Ghost-1 stays available through the API and the humanizer's model settings.
Frequently asked questions
Ghost-2 is the second generation of UndetectedGPT's proprietary humanization model. It rewrites AI-generated text so it bypasses AI detectors like GPTZero, Originality.ai, ZeroGPT, Turnitin, Quillbot, and Grammarly while keeping your original meaning, references, and citations intact.
Yes. Ghost-2 is now the default everywhere, but Ghost-1 stays available: API users can pin it with the model parameter, and subscribers can switch models in the humanizer settings. Previous generations stay online so a new release never breaks your workflow.
Ghost-2 is benchmarked against the strictest AI detectors on the market: GPTZero, Originality.ai, ZeroGPT, Turnitin, Quillbot, and Grammarly. It runs the exact same eval as Ghost-1 and passes with a 98.3% average pass rate, up from 96.2%. Other detectors tend to be similar or easier to bypass.
No. Ghost-2 rewrites how something is said, not what is said. Your original meaning, structure, references, and citations are preserved.