We make Hemmingway, so we put it first, and here is why. Hemmingway-1.5 is a model that writes the text itself, and in our own published test 90% of its writing passed GPTZero and four other top AI detectors on the first try, more often than the 86% that real human writing got. The other tools people mean by undetectable AI are humanizers: you write with another AI, paste the text in, and they rewrite it. Undetectable AI, StealthGPT, WriteHuman, HIX Bypass, Humbot, BypassGPT and QuillBot's AI Humanizer are the best known. We have not tested any of them, so we describe each from its own site, as it read on 27 October 2026.
Our page on undetectable AI has Hemmingway-1.5's full result.
The short list
- Ours, to write it in one step: Hemmingway-1.5. It writes the email, the post or the story, and it rewrites AI text you paste in. Free to try, and its weights are open.
- A humanizer with its own detector and writing tools: Undetectable AI. Its free trial is limited to 250 words.
- A humanizer that scores each sentence: WriteHuman. Its built-in detector marks each sentence with how likely it is to be AI.
- A study bundle with a humanizer in it: Humbot. It sits next to a homework helper, flashcards and a citation tool.
- A quick rewrite of a short AI draft: QuillBot's AI Humanizer, next to its paraphraser. Its own page says it is not a tool for evading AI detection.
- The ones that sell the bypass hardest: StealthGPT, HIX Bypass and BypassGPT. All three pitch students and assignments.
Side by side
| Tool | What it is | Starts from | What its own site claims about detectors | Free use |
|---|---|---|---|---|
| Hemmingway-1.5 (ours) | A writing model and app | Your request, or text to rewrite | 90% passed GPTZero and four other detectors in our test, method published | Free to try, no card |
| Undetectable AI | Humanizer, detector and writing tools | AI text you paste | Scores as human on "every major detector"; names none on its home page | Free trial up to 250 words |
| WriteHuman | Humanizer with a detector | AI text you paste | Prints its own scores for eight detectors | A free trial |
| StealthGPT | Humanizer and a writer | AI text, or a prompt | Names Turnitin, GPTZero and ten others; prints its own scores | A small free tier |
| HIX Bypass | Humanizer | AI text you paste | Lists GPTZero, Originality.ai, Copyleaks and others | A free trial |
| Humbot | Study tools with a humanizer | AI text you paste | Names Turnitin, Originality.ai, GPTZero, ZeroGPT and Copyleaks | A free trial for new users |
| BypassGPT | Humanizer | AI text you paste | Names ZeroGPT, GPTZero and Originality.ai | Free to try |
| QuillBot AI Humanizer | Humanizer next to a paraphraser | An AI draft | Says it is not a tool for evading AI detection | Short texts, with limits |
Every claim in the right-hand columns is the tool's own. None of them is a result of ours, except the first row.
Why we put Hemmingway-1.5 first
Because it is the only one here whose result comes with a published method. We had it write 1,848 texts in 13 kinds of writing, at all four thinking levels, and ran each once through GPTZero, Fakespot, Vanguard, WasItAIGenerated and MELD. No picking, no retries. 90% passed. We ran 1,670 texts by people through the same detectors as a yardstick, and 86% passed. The full write-up is in our AI detector test.
The other reason is the step it saves. A humanizer needs a draft from somewhere else first. Hemmingway-1.5 writes the draft, and what it writes is meant to read as a person's from the start. It can still rewrite: paste in text from ChatGPT and ask for it in a person's voice. On the model's Hugging Face card, 89% of its rewrites of AI text passed the same detectors.
Undetectable AI
Undetectable AI's site describes three main things: an AI detector, a humanizer that rewrites stiff text so it reads naturally, and an AI image detector. Its menus also list a paraphraser, an essay writer and a plagiarism checker. Its home page says the humanizer's output scores as human on every major detector, without naming them. Its pricing page showed plans from $9.99 a month for 10,000 words, or $5 a month billed yearly, and a free trial limited to 250 words. Hemmingway vs Undetectable AI puts the two side by side.
WriteHuman
WriteHuman says it rewrites text from ChatGPT, Claude, Gemini and other models, changing sentence length, word choice and cadence while keeping the meaning. It has a built-in detector that scores each sentence, and it prints its own scores for eight detectors, Turnitin and GPTZero among them. Its plans were listed at $12, $19 and $39 a month.
StealthGPT
StealthGPT has a humanizer and a writer that drafts essays with citations. It names twelve detectors it says it beats, Turnitin and GPTZero among them, and prints its own scores. It markets a browser extension for quiz, test and homework answers.
HIX Bypass
HIX Bypass calls itself an undetectable AI tool that rewrites AI text, and says it does more than swap phrases. It lists GPTZero, Originality.ai, Copyleaks, ZeroGPT and others. Its page pitches drafts for essays and assignments that get past AI detection and plagiarism checks.
Humbot
Humbot sells itself as a study and writing assistant: a humanizer next to an AI detector, a plagiarism checker, a homework helper and flashcards. It says its output passes Turnitin, GPTZero and others, and shows no test results for that on its home page.
BypassGPT
BypassGPT calls itself an AI bypasser that rewrites content into undetectable AI writing. It names ZeroGPT, GPTZero and Originality.ai, and says it is free to try. Its student section talks about submitting assignments with confidence.
QuillBot's AI Humanizer
QuillBot's humanizer rewrites AI drafts to improve tone, clarity and flow, next to its paraphraser and grammar checker. Its own page says it improves how writing reads and is not a tool for evading AI detection. The free version handles short texts. The best AI humanizers covers it and Grammarly's humanizer in more detail.
How we chose
We make Hemmingway. Our numbers are the ones on the model card. For every other tool we read its own site on 27 October 2026 and describe only what it says; prices and free limits change, so check before you rely on one. We have not tested Undetectable AI, StealthGPT, WriteHuman, HIX Bypass, Humbot, BypassGPT or QuillBot, so we do not rank them against each other.
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Common questions
What is the best undetectable AI?
We put Hemmingway-1.5 first, and we make it. In our published test, 90% of its writing passed GPTZero and four other AI detectors on the first try, and it writes the text itself, so there is no second tool. Humanizers such as Undetectable AI, WriteHuman and StealthGPT rewrite text from another AI instead. We have not tested them.
Is there an AI that passes every AI detector?
In our test, 90% of Hemmingway-1.5's writing passed GPTZero and four other AI detectors on the first try. Writing by real people passed 86% of the time, so detectors flag some human writing too.
What is the difference between an undetectable AI writer and a humanizer?
A writer writes the text from your request. A humanizer takes text another AI wrote and rewrites it. Hemmingway-1.5 does both: it writes from scratch, and it rewrites AI text you paste in.
Is there a free undetectable AI?
Hemmingway is free to try with no card. Undetectable AI's free trial covers 250 words, and WriteHuman, HIX Bypass, Humbot, BypassGPT and QuillBot each have a free trial or a small free tier, by their own pages.