By The best free humanizer to experiment with, and a hard sell once it asks for $20. Ten free runs a day and click-to-swap sentence alternatives make StealthWriter the right place to learn whether humanizing works on your writing. The paid plans sell daily caps most writers never reach, detector results range from mixed to poor, and the output needs more editing than anything else on our list.
- Best for
- Testing humanizers for free, and editors who rework text sentence by sentence
- Skip if
- You need an API, readable output without editing, or anything that has to survive GPTZero
- Price
- Free; paid from $20/mo for 50 runs a day
- Trustpilot
- 3.2 from 56 reviews
What StealthWriter is, and the LLC behind it
StealthWriter does two jobs in one browser tab. The humanizer rewrites AI-generated text at light, medium or aggressive strength using the company's own engines, currently Ghost 5.2 Mini, Ghost 5.2 Pro and a set of Legacy models. The detector, which it calls V1 and V2, scans text sentence by sentence and colours the lines it thinks are machine-written. The two are joined up, so you can humanize, scan, then click any sentence that still looks suspect and pick from several alternative rewrites of just that line.
That last feature is the reason the tool is on our list. Every other humanizer we cover treats rewriting as one shot: paste, click, accept or re-roll the whole thing. StealthWriter lets you keep the sentences you like and replace the ones you do not, which is how editors actually work.
The company behind it is AiVantage LLC. Its terms are governed by Wyoming law, the support line carries a 307 area code, and support hours are listed in Mountain Time. No founders, funding or headcount are disclosed, and the homepage claims only that "thousands of writers" use it, which is refreshingly modest for this category. It is web-only. The FAQ says plainly that there is no public API, and supported languages include Spanish, French, German, Italian, Portuguese and Dutch alongside English.
The tests we trusted, and the ones we threw out
A surprising number of ranking StealthWriter reviews describe a product that no longer exists. GPTZero's February 2026 review and ToolsForHumans both quote Basic, Standard and Premium tiers at $20, $35 and $50. Another 2026 review lists $29 and $79 plans priced by monthly words, which match nothing on the pricing page we loaded. Winston AI's test dates from December 2023, several engine generations ago. We kept older tests where they show a pattern and labelled their age.
Our sources: the vendor's pricing page, FAQ, terms and refund policy, read on October 7, 2026; GPTZero's own test, published February 11, 2026; Winston AI's test from 2023; a 2026 review by Fast.io that reported scores against three detectors; the HumanizerBench leaderboard updated October 1, 2026; iTechGuides' product page, fact-checked September 20, 2026; and the Trustpilot profile for stealthwriter.ai.
One small trap if you do your own homework: there is a second, smaller Trustpilot listing under a different domain, and at least one review we read quoted its 2.1 score as if it were this company's. The listing for stealthwriter.ai is the one with 56 reviews.
Detector results: mostly caught by the detectors that matter
StealthWriter's homepage makes no explicit claim about beating particular detectors, and its affiliate rules forbid partners from calling it "undetectable", a "detector-bypass tool", or saying it passes any specific detector. For a product called StealthWriter that is a striking amount of restraint. The independent evidence suggests it is also wise.
GPTZero's test took a Claude-written press release, humanized it, and ran both versions through several detectors. GPTZero scored the original and the rewrite at 100 percent AI, calling the second "likely an AI paraphrased version" of AI text. In the same test the rewrite fooled Copyleaks and QuillBot. GPTZero sells a detector, so its verdict on its own product is not neutral (our GPTZero review covers its own accuracy problems), but the result lines up with others.
Fast.io's 2026 review ran Ghost 5.2 output against three detectors and reported GPTZero at 100 percent AI, Originality.ai at 28 percent AI on an essay, and Turnitin at 16 percent AI, which the reviewer called a narrow pass against a typical 20 to 25 percent threshold. It also counted 4.2 grammar errors per 1,000 words. Winston AI's older test found the rewrite still scored 0 percent human on its detector, and quoted the tool turning "mosaic of conflicting ideologies" into "jigsaw puzzle of different thoughts".
On HumanizerBench, which scores 14 humanizers across six detectors including GPTZero, Originality.ai and Pangram, StealthWriter posted a bypass score of 71.3 and finished 8th overall on 65.98, ahead of Walter Writes in 10th and behind Undetectable AI in 3rd. The benchmark is run by WriteHuman, a competitor that ranks itself first, though it publishes every input, output and detector response.
Put together: StealthWriter does change what cheaper detectors see. Against GPTZero, the detector most teachers and many editors use, it has failed every published test we found. A small Substack test of six humanizers adds that StealthWriter cleared two of three detectors on one passage and not on a second passage from the same document, which is the inconsistency everyone in this category should expect.
Sentence-by-sentence editing, and the readability bill
The alternatives feature is excellent. You click a sentence, a short list of rewrites appears, and you choose one or leave the original. On a 1,000-word piece you might swap eight or ten lines and leave the rest alone, which keeps your voice in the parts that already sounded like you.
You will need it, because the default output is rough. HumanizerBench gave StealthWriter a readability score of 41.8, the lowest of all 14 tools it tested, against 63.5 for Walter Writes and 63.9 for Undetectable AI. Meaning preservation was middling at 71.6, and the benchmark docked it for meaning drift. Fast.io found that aggressive mode could flip a claim entirely, turning a study that "found no significant correlation" into text that implied the opposite. That is the failure that should worry anyone humanizing factual content, because a detector will not catch it and a reader might.
So the honest description is a tool that produces a rough draft quickly and gives you good controls for fixing it. If you like working sentence by sentence, that is a fair trade. If you want to paste, click and publish, it is the wrong tool.
Daily caps, not word counts: the pricing explained
StealthWriter prices by runs per day rather than words per month, which makes it hard to compare with everyone else. As of October 7, 2026 the plans look like this. Humanizations and detector scans have separate, equal daily allowances.
| Plan | Monthly | Humanizations a day | Detector scans a day | Words per input | Engines |
|---|---|---|---|---|---|
| Free | $0 | 10 | 10 | 1,000 | Ghost 5.2 Mini |
| Starter | $20 | 50 | 50 | 5,000 | Mini, Pro, Legacy |
| Plus | $50 | 150 | 150 | 5,000 | Mini, Pro, Legacy |
| Pro | $100 | 350 | 350 | 5,000 | Mini, Pro, Legacy |
| Business | $200 | 800 | 800 | Not stated | All |
| Scale | $400 | 2,000 | 2,000 | Not stated | All |
| Enterprise | Custom billing and procurement | ||||
The yearly toggle says "Save 17%" but did not show us annual totals. iTechGuides, checking on September 20, 2026, lists Starter at $200 a year, which works out to about $16.67 a month.
Now the arithmetic. Take a freelance writer producing 20 articles a month at 1,500 words, about 30,000 words. Allow three humanize runs per article once you count re-rolls, and the free plan's 1,000-word input limit means each article goes in as two halves, so call it six runs per article and 120 a month, or about six per working day. The free plan's ten a day covers that, provided you can live with Ghost 5.2 Mini and the splitting. Upgrading buys the Pro engine and the 5,000-word input limit for $20 a month. Walter Writes would charge $8 a month, billed yearly, for the same 30,000 words.
Scale it up and the picture flips. An agency pushing 300,000 words a month in 2,000-word pieces handles about 150 pieces, roughly seven a working day. Even at three runs each that is around 22 runs a day, comfortably inside Starter's 50. So $20 covers a workload that would need Walter's $99 Teams plan. The daily structure only bites on bursty work: a deadline day with 60 runs hits the ceiling, and a quiet Monday does not bank anything for Friday.
In short, StealthWriter is expensive for light users, oddly cheap for steady heavy users, and awkward for anyone whose workload comes in spikes.
Why the free plan is the best in the category
Ten humanizations and ten detector scans a day, each up to 1,000 words, with the deep scan and Ghost 5.2 Mini included. No card is needed. Compare that with 250 words once at Undetectable AI or 300 words once at Walter Writes, and the gap is not close.
What makes it useful is that a week of it is a real experiment. Take five pieces of your own AI-assisted writing, humanize each a couple of times, run the results through the detector your editor or client uses, and read them aloud. By Friday you will know whether humanizing helps your writing at all, which is the question every paid plan in this category asks you to answer on trust. The limits are the engine and the cap: Ghost Mini is the weaker model, and the 1,000-word input limit means long pieces go in sections.
Complaints: cancellation, card details and silence
As of October 7, 2026, StealthWriter holds 3.2 out of 5 on Trustpilot from 56 reviews, 39 of them from the last twelve months. The split is stark, 37 percent five-star and 57 percent one-star, with almost nothing in the middle. The five-star reviews often name a support agent who sorted a problem quickly. The one-star reviews are dominated by cancellation:
"DONT BUY THIS as there is no option to UNSUBSCRIBE OR REMOVE CARD DETAILS."
Trustpilot reviewer, stealthwriter.ai profile
The terms say you may cancel at any time and that unrenewed plans simply lapse, so we read that complaint as a hard-to-find setting rather than a missing one. Other recurring themes are inconsistent rewrite quality, unclear explanations of what counts against the daily limits, and support requests that go unanswered. Trustpilot shows the company has not replied to its negative reviews, the opposite of Walter Writes, which answers most of them within a day.
Reviewer scores elsewhere are lukewarm. iTechGuides gives it 5.6 out of 10, 20th of 24 in its paraphrasing category, citing the $20 starting price, the missing API and the daily limits. ToolsForHumans gives it 2.5 out of 5 and calls the free tier "genuinely useful for testing". Capterra has no user reviews at all.
Refunds, academic rules and your data
The refund policy allows a request within 24 hours of a purchase or renewal, provided you have not used the account since paying. That is short, but it covers renewals, which Walter Writes does not, so an unwanted auto-renewal is recoverable if you catch it the same day. Anything beyond that is at the company's discretion through the contact page.
Use one humanization after a renewal and the refund is gone. If you are planning to cancel, do it before the renewal date rather than relying on the 24-hour window.
The terms say the service "must not be used for academic dishonesty or cheating", which explicitly includes submitting AI content as your own and misleading plagiarism detectors. Students should take that literally. It means the company has written itself out of any dispute you end up in, and it means a flagged essay is your problem and the policy says so. Text is processed on StealthWriter's servers like every tool here, and with no API there is no way to keep it inside your own systems.
How it compares with Walter Writes, Undetectable AI and Phrasly
| StealthWriter | Walter Writes | Undetectable AI | Phrasly | |
|---|---|---|---|---|
| Cheapest paid | $20/mo | $8/mo billed yearly | $9.99/mo; $5 annual | $10.99/mo annual |
| Volume | 50 runs/day, 5,000 words each | 30,000 words/mo | 10,000 words/mo | Unlimited, 5,000 per run |
| Free tier | 10 runs/day, 1,000 words | 300 words, once | 250 words, once | $2 three-day trial |
| Sentence alternatives | Yes | No | No | No |
| API | No | MCP server | Yes | No |
| HumanizerBench readability | 41.8 | 63.5 | 63.9 | 44.2 |
If you want readable output with the least editing, Undetectable AI is the better rewrite engine and cheaper at low volume. If you process a moderate, predictable amount each month, Walter Writes is far cheaper per word and comes with an MCP server for assistant workflows. Phrasly has the highest bypass score on HumanizerBench but weak readability and meaning scores, closer to StealthWriter's profile than to the leaders'. StealthWriter wins on the free plan and on editing control, and the full humanizer ranking puts it third for exactly those reasons.
Who should open an account, and who should not
Everyone curious about humanizers should open a free account. It costs nothing, the limits are generous, and it will tell you more about your own writing in a week than any review can. Editors who already rework drafts line by line will also like the paid plans, because the alternatives feature suits that habit better than any rival.
Pay for it if your volume is steady and high, you need 5,000-word inputs, and you are happy to edit every output. Skip the paid plans if you write a few thousand words a month, if you need an API, if your work has to pass GPTZero, or if you are a student looking for a way around a policy. The policy will still apply, and StealthWriter's own terms will not be on your side.
Bottom line. Use the free plan as a testing lab. Pay $20 only if the sentence editor has become how you work, because the rewrite engine on its own is not good enough to justify it.
StealthWriter questions, answered briefly
Is StealthWriter free?
Yes. Ten humanizations and ten detector scans a day, up to 1,000 words each, on the Ghost 5.2 Mini engine.
What do the paid plans cost?
$20 a month for 50 runs a day, rising to $400 for 2,000. Yearly billing saves 17 percent.
Does it beat GPTZero?
Not in GPTZero's own February 2026 test, which scored the output 100 percent AI before and after. Weaker detectors were fooled.
Is there an API?
No. Its FAQ says it is web-only with no public API.
Can I get a refund?
Within 24 hours of a purchase or renewal, and only if you have not used the account since paying.
Who owns it?
AiVantage LLC, under Wyoming law. The founders are not named publicly.
Is the built-in detector reliable?
Use it for the sentence highlighting, not as a verdict. Reviewers report its scores disagree with third-party detectors.
Verdict
StealthWriter is two products with one login. The free plan is the most generous in the category and the sentence-level editor is a genuinely better way to fix machine-sounding text. The paid product is a rewrite engine that scored lowest for readability in the one public benchmark that measures it, fails against GPTZero in every published test we found, and sells its capacity in daily caps that suit almost nobody's real workload except a busy agency's.
We give it 3.1. Open the free account this week, run your own writing through it, and pay only if you find yourself reaching for the alternatives panel every day.