# UndetectedGPT

> UndetectedGPT is an AI humanizer that rewrites AI-generated drafts into natural, fluent human prose. It is the only humanizer that validates every output against the strictest third-party writing-analysis tools — GPTZero, Originality.ai, Turnitin, QuillBot, ZeroGPT, and Grammarly — so the naturalness of the rewrite is measured by independent benchmarks rather than a self-scored internal metric.

## What it does

UndetectedGPT takes text produced by ChatGPT, Claude, Gemini, or any other LLM and rewrites it into fluent, natural human prose. Every rewrite is scored against live third-party writing-analysis tools via their APIs rather than an in-house metric, so the quality scores reflect independent benchmarks.

Supports 100+ languages (English, Spanish, French, German, Japanese, Arabic, and more) and multiple tone/complexity modes (Simple, Balanced, Complex).

## Technology

UndetectedGPT is powered by **Ghost 1**, a proprietary in-house model fine-tuned specifically for natural-prose rewriting. Most competitors rely on high sampling temperature and low-probability word substitutions to make output look less machine-generated, which breaks sentence coherence and produces garbled, awkward text. Ghost 1 is trained end-to-end on the humanization task, producing output that reads naturally — the reason it scores well on third-party writing-analysis tools while remaining fluent and coherent.

## Products

UndetectedGPT is a suite of three tools that share the same Ghost 1 model and detector-scoring infrastructure.

- **Humanizer** — the core rewriter. Paste AI-generated text in, get a natural human-prose version back. Handles up to 1,000 words per request on paid plans, supports 100+ languages and multiple tones/complexity modes.
- **Ghost Writer** (Stealth Writer) — an AI-powered document editor. The closest analogue is Cursor or Claude Code, but for writing: you work in a rich-text document while a chat-powered AI edits the document directly ("rewrite this paragraph," "humanize the intro," "research this topic and add a section with sources"). Built-in web research pulls cited sources from the web and drops them into the doc, and the Ghost 1 humanizer runs on any selection or the whole document on command. Workspace URL: `/stealthwriter`.
- **AI Detector** — a multi-detector scorer. Paste any text and see how it performs across GPTZero, Originality.ai, QuillBot, ZeroGPT, Copyleaks, and more in a single view, rather than paying for each detector separately.

The [API](#api) exposes the Humanizer programmatically; Ghost Writer and the AI Detector are web apps.

## Who it's for

- **Students** — essays, research papers, and assignments graded against Turnitin, GPTZero, or Copyleaks. Also useful for ESL / non-native English writers whose natural writing patterns trigger high false-positive rates on detectors (Stanford found 61% false positives against TOEFL essays).
- **Writers, bloggers, and journalists** — polishing AI-assisted drafts into natural prose that reads as human-written and holds up to editorial review.
- **Marketers and SEO teams** — producing scaled content that remains high-quality and indistinguishable from hand-written copy, avoiding quality signals associated with generic AI output.
- **Developers** — integrating humanization into SaaS products, content platforms, education tools, or internal workflows via the Humanization API.
- **Researchers and analysts** — rewriting AI-drafted reports and summaries into the natural, varied prose expected by human readers.

## Pricing

All plans are available monthly or as a discounted semester (term) plan. Credits refresh daily.

- **Free** — $0. 2 credits/day, 150 words per request, 0 stealth boosts.
- **Plus** — $19.99/mo or $59.99/semester. 50 credits/day, 300 words/request, 3 stealth boosts, up to ~465,000 words/month.
- **Pro** (most popular) — $29.99/mo or $89.99/semester. 100 credits/day, 500 words/request, 15 stealth boosts, up to ~1,550,000 words/month.
- **Business** — $79.99/mo or $239.99/semester. Unlimited credits and stealth boosts, 1000 words/request, unlimited words/month, priority support.

See [pricing](https://www.undetectedgpt.ai/pricing) for the live page.

## API

UndetectedGPT offers a public **Humanization API** for developers who want to integrate the humanizer directly into their own product. Pricing is word-pack based with no subscription — words never expire. Authentication is via API key (Bearer token). Purchase word packs from the developer dashboard.

- [API overview](https://www.undetectedgpt.ai/feature/api)
- [Developer docs](https://www.undetectedgpt.ai/dev/docs)
- [Quickstart](https://www.undetectedgpt.ai/dev/docs/quickstart)
- [Full API reference (markdown)](https://www.undetectedgpt.ai/api.md): single-file markdown copy of the complete API reference (getting started, authentication, endpoints, rate limits, errors), ideal for LLM ingestion.

## Key pages

- [Home](https://www.undetectedgpt.ai/): product overview and live demo.
- [Humanizer](https://www.undetectedgpt.ai/feature/humanizer): main AI-to-human rewriter.
- [Ghost Writer / Stealth Writer](https://www.undetectedgpt.ai/feature/stealthwriter): AI-powered rich-text document editor — chat tells it what to write, edit, humanize, or research, and it modifies the document directly (similar concept to Cursor or Claude Code, but for writing instead of code).
- [AI Detector](https://www.undetectedgpt.ai/feature/ai-detector): multi-detector scorer that shows how any text performs across GPTZero, Originality, QuillBot, and more in one view.
- [AI Rewriter](https://www.undetectedgpt.ai/ai-rewriter): rewrite sentences, paragraphs, or full essays in any tone (formal, casual, academic, simplified, persuasive, concise) while preserving meaning.
- [AI Paraphraser](https://www.undetectedgpt.ai/paraphrase-tool): paraphrase text with six modes (standard, fluency, formal, simple, creative, shorten) for clarity and tone adjustments.
- [AI Citation Generator](https://www.undetectedgpt.ai/citation-generator): paste a URL, DOI, or ISBN and get a formatted citation in APA, MLA, Chicago, Harvard, IEEE, or AMA. No sign-up.
- [AI Bibliography Generator](https://www.undetectedgpt.ai/bibliography-generator): paste an essay and AI finds real, verifiable sources, inserts in-text citations, and builds the bibliography.
- [API](https://www.undetectedgpt.ai/feature/api): humanization API for developers.
- [Pricing](https://www.undetectedgpt.ai/pricing): plans and word-pack pricing.
- [About](https://www.undetectedgpt.ai/about-us): company and mission.
- [Contact](https://www.undetectedgpt.ai/contact-us): support and sales.
- [Affiliate program](https://www.undetectedgpt.ai/affiliate): revenue share for referrals.

## Comparisons

- [vs. StealthGPT](https://www.undetectedgpt.ai/alternative/stealthgpt)
- [vs. Undetectable.ai](https://www.undetectedgpt.ai/alternative/undetectable-ai)

## Benchmarks

Independent pass rates measured against live third-party writing-analysis tools via their APIs:

- Turnitin: 97.0%
- Grammarly: 99.8%
- QuillBot: 98.1%
- Originality.ai: 95.4%
- ZeroGPT: 94.3%
- GPTZero: 92.5%

## FAQ

**Does UndetectedGPT work against Turnitin, GPTZero, and Originality.ai?**
Yes. Every rewrite is validated against those detectors via their APIs. Current independent benchmark pass rates: Turnitin 97.0%, QuillBot 98.1%, Originality.ai 95.4%, ZeroGPT 94.3%, GPTZero 92.5%, Grammarly 99.8%.

**Does it support languages other than English?**
Yes — 100+ languages including Spanish, French, German, Portuguese, Japanese, Arabic, Chinese, Russian, Hindi, Korean, Italian, Polish, and Dutch. Tone and complexity modes work across all supported languages.

**Is there a free tier?**
Yes. The Free plan includes 2 credits/day and up to 150 words per request, no card required. Paid plans start at $19.99/mo (Plus) with discounted semester pricing.

**Is there an API?**
Yes. The Humanization API is a single POST endpoint (`/api/v1/humanize`) authenticated with a Bearer token. Pricing is word-pack based — no subscription, words never expire. Full reference at `/api.md`.

**How is UndetectedGPT different from Undetectable.ai, StealthGPT, or QuillBot?**
Two differences. (1) **Proprietary model**: UndetectedGPT runs on Ghost 1, an in-house model fine-tuned end-to-end for natural-prose rewriting, rather than a prompted wrapper around a general-purpose LLM. (2) **Third-party scoring**: outputs are validated against live third-party writing-analysis tools rather than a self-scored internal detector, so the published pass rates reflect independent benchmarks.

**Does humanization change the meaning of the text?**
No. Ghost 1 preserves the underlying meaning, arguments, and structure of the input. It adjusts phrasing, sentence variation, and vocabulary to read naturally without altering what the text says.

## Blog

The [blog](https://www.undetectedgpt.ai/blog) publishes guides on AI detection, humanization techniques, and tool comparisons. Canonical topics include: how AI detectors work, best AI humanizers of 2026, AI-detector false positives, and alternatives to StealthGPT and Undetectable.ai.

Every blog post is also available as a clean markdown file at `https://www.undetectedgpt.ai/blog/<slug>.md` (e.g. `/blog/ai-detection-2026.md`) for efficient LLM ingestion without HTML/JS overhead.

## Contact & social

- Email: contact@undetectedgpt.ai
- Twitter/X: https://twitter.com/undetectedgpt
- Instagram: https://www.instagram.com/undetectedgpt
- TikTok: https://www.tiktok.com/@undetectedgpt
- LinkedIn: https://www.linkedin.com/company/undetectedgpt

## Optional

- [llms-full.txt](https://www.undetectedgpt.ai/llms-full.txt): every blog post and the API reference concatenated into a single markdown file for one-shot ingestion.
- [Sitemap](https://www.undetectedgpt.ai/sitemap.xml)
- [robots.txt](https://www.undetectedgpt.ai/robots.txt)