Undetectable AI and StealthGPT are two of the better known AI humanizer tools. Both take AI-generated text and rewrite it to read as human, and both include an AI detector so you can check the score before using it. Both also say they can beat detectors such as Turnitin, GPTZero and Originality.ai. This comparison is built from both companies’ pricing pages, checked on 27 October 2026. I have not run either tool against a detector, so I can’t confirm any bypass rates, and you should treat them as vendor claims.
Should you use an AI humanizer tool at all?
It is worth being clear about this. AI detectors are imperfect in both directions: they miss some AI text and flag some human text. Humanizers exploit that, and the detector makers keep updating their models in response, so any bypass is temporary. For students, using a humanizer to submit AI-written work as your own breaks most academic integrity policies whether or not Turnitin flags it. Where AI help is allowed (marketing copy, SEO drafts, your own writing that a detector wrongly flags), these tools are easier to justify.
Undetectable AI features
- AI humanizer with writing level matching, so the output can be pitched at a particular reading level.
- Unlimited AI detecting on paid plans.
- Unlimited use of its Human Auto Typer.
- API compatibility listed on every plan.
- A business option with custom pricing, non-expiring credits, white labelling and a Smart Job Applier tool.
- A money-back promise: if anything it produces is flagged as not human, Undetectable AI says it will refund the cost of that humanization (its help pages give the conditions).
Its pricing page also leads with a claim that it was rated the number one AI detector by Forbes. I have not checked that article, so I would not weigh it heavily.
StealthGPT features
- AI humanizer and AI detector on every plan, with history.
- In-text citations and Stealth Insights.
- 100+ languages, file upload (PDF and images from Max up), an iOS app and a Chrome extension.
- MCP access for using StealthGPT inside Claude, Cursor and similar tools.
- Team seats on Max (3) and Enterprise (5); API and custom fine-tuned models on Enterprise.
StealthGPT’s page says its newest model beats Pangram and other major AI detectors, and that it has 1.5 million active users.
Undetectable AI vs StealthGPT pricing
| Words a month | Undetectable AI (monthly / yearly per month) | StealthGPT (monthly) |
|---|---|---|
| 10,000 | $9.99 / $5.00 | None |
| 20,000 | $19.00 / $9.50 | None |
| 35,000 | $31.00 / $15.75 | None |
| 50,000 | $42.50 / $21.25 | Pro $29.99 (1,000 words per request) |
| 200,000 | Higher tiers up to 380,000 words | Max $49.99 (2,000 words per request, 3 seats) |
| 1,000,000+ | Business: custom | Enterprise $179.99 (API, 5 seats) |
For small volumes, Undetectable AI is clearly cheaper, especially billed yearly at 50% off. At 50,000 words a month the monthly prices are closer, and StealthGPT’s Max plan becomes better value per word than Undetectable AI’s mid tiers if you need around 200,000 words. StealthGPT saves up to 17.5% on yearly billing.
Turnitin, GPTZero, Originality and other AI detectors
Both tools name the big AI detectors in their marketing. Neither publishes an independent test, and the results will depend on the text, its length, the topic and the detector version. Undetectable AI’s refund promise is the only concrete commitment I found on either pricing page, though it refunds the humanization cost rather than covering any wider consequences.
If you’re going to use one, test it on your own writing and check the result with the exact detector you’re worried about. Also read the output carefully. A humanizer that passes a detector but introduces mistakes, changes facts or makes the writer sound unlike themselves has not done its job.
What an AI detection score really tells you
Both tools show an AI detection score after humanizing, and it is easy to read too much into it. A score from a humanizer’s own built-in detector is not the same as a score from the detector your teacher, client or publisher uses. Each AI detection tool is trained differently, so the same text can score very differently from one detector to the next.
The vendors themselves describe AI text in terms of patterns: predictable phrasing, uniform sentence rhythm and stock transitions. Text written by ChatGPT and similar models often has those patterns, and a humanizer tries to break them up. That also explains why short pieces are harder to judge, as there is less text for any detector to work with.
If you write your own work and a detector wrongly flags it, a humanizer is the wrong fix. Keeping drafts and version history is better evidence that you wrote it yourself.
Feature comparison for writers and teams
Looking at the two side by side as an AI tool for regular writing work, the differences are fairly clear. Undetectable AI is built around simple word-based plans for an individual writer, with writing level matching and an API listed on every plan. StealthGPT is built for heavier use, with longer requests on higher plans, file upload, citations for academic-style writing, team seats and MCP access. If you share an account with colleagues, StealthGPT is the only one of the two with seats on its standard plans.
Ease of use
Both follow the same flow: paste the text, humanize, check the AI score. StealthGPT has more ways to use it (iOS app, Chrome extension, MCP) and more extras for longer documents. Undetectable AI’s writing level matching is useful if you want the output to match a particular audience.
Limits and drawbacks
- Undetectable AI’s free trial is limited to 250 words.
- Undetectable AI’s lower tiers are small (10,000 words is a few essays).
- StealthGPT has no free plan listed and limits Pro to 1,000 words per request.
- Both rely on bypass claims that can change with any detector update.
Conclusion and verdict
For an individual writer who wants to try a humanizer without a big commitment, Undetectable AI is the better starting point: cheaper, a free trial and a refund promise. For teams, very long documents or people who want the tool inside Claude or Cursor through MCP, StealthGPT has the more complete feature set. Either way, I would not rely on any AI humanizer for work where getting flagged would have serious consequences.
Alternative AI writer tools
- StealthWriter: a free plan with 10 humanizations a day.
- Rephrasy: cheaper yearly plans and a lifetime deal.
- WriteHuman: per request plans from $12 a month billed yearly.
