Walter Writes vs. Undetectable AI: which AI humanizer is better for students?

Undetectable AI and Walter Writes look remarkably alike. Both offer the same five readability levels, from High School to Marketing, a menu of writing purposes, a built-in AI detector and a ladder of stronger “bypass” settings. Undetectable AI got there first, in 2023. Walter Writes, from Walter AI Inc. in Montreal, followed in mid-2024 at a much lower price.

So is the extra cost of the older tool worth it? We ran both through the same samples and detectors, then compared everything around the humanizer: price, free access, refunds, privacy and track record.

At a glance

Prices and policies as published by each company on October 26, 2026.

How we compared them

We ran both tools through the same hands-on test on October 20, 2026, and checked their published terms on October 26.

The samples. We used five texts of about 500 words, each written by an AI chatbot:

1. An argumentative college essay (ChatGPT)
2. The discussion section of a lab report, with figures and an APA citation (Claude)
3. A professional email (Gemini)
4. A blog post (ChatGPT)
5. A Spanish-language opinion piece (Gemini)

They’re the same samples we used across our humanizer coverage.

The settings. We paid for each tool’s mid-priced monthly plan: Undetectable AI’s 20,000-word plan ($19) and Walter Writes Pro ($23). Because the two tools have such similar controls, we could match their settings closely:

• Undetectable AI: its top Undetectable mode at University readability, with the matching purpose (Essay, Report, Business Material or Article) and Balanced strength.
• Walter Writes: the Standard bypass level at University readability, with the matching purpose (Essay, Report, Business or Blog).

Some samples got one retry in each tool’s strongest setting: More Human strength for Undetectable AI, the Enhanced level for Walter Writes. Where we retried a sample, we report the retry’s results.

The detectors. We used seven: GPTZero, Originality.ai, Copyleaks, ZeroGPT, Winston AI, QuillBot’s AI detector and Pangram, a newer detector that several humanizer companies now name in their marketing.

• Pass threshold: a check counts as a pass if the detector labels the text human-written or rates it less than 20% likely to be AI.
• Checks per tool: 35 (five samples, seven detectors).
• Turnitin: not included. It’s sold only to schools.

Quality. Two editors read each pair of outputs blind, without knowing which tool produced which, and rated how well each kept the original meaning, from 1 to 5. We also:

• noted every new problem each tool introduced, from grammar errors to awkward wording,
• checked that every number, name and citation survived,
• measured Flesch Reading Ease, where a higher score means easier to read.

The rounds. We compare the two tools in nine rounds. The first two are tested. The other seven come from each company’s published prices, terms and policies, and from public ratings.

How we pick a winner. A humanizer’s main job is getting text past AI detectors, so the detector round decides the verdict: the tool that passes more of the 35 checks wins. Two safeguards apply:

• Meaning comes first. A tool whose rewrites average below 3.5 out of 5 on our blind meaning check can’t win on detector results, because text that passes a detector by losing your argument isn’t usable.
• Close calls go to quality. If the two tools finish within two checks of each other, the writing-quality round decides.

The other rounds don’t change the winner, but they show who might prefer the runner-up.

Round 1: AI detector results (decides the verdict)

Winner: Undetectable AI

Before humanizing, all 35 checks flagged our samples as AI-written. Undetectable AI passed 13 of the 35 checks (37%), and Walter Writes passed 6 (17%). Undetectable AI finished ahead on six of the seven detectors; on Pangram, neither got a single sample through. Both did best on ZeroGPT and with the email, and neither got our Spanish sample past a single detector, even after a retry. Undetectable AI needed a retry on two samples, the lab report and the Spanish piece. Walter Writes needed three: the essay, the lab report and the Spanish piece.

Both companies promise more than their terms do:

• Undetectable AI says its top mode “bypasses 99+% of detectors.”
• Walter Writes says it helps text “bypass Turnitin, GPTZero, Originality.ai.”
• Their terms: both say they don’t guarantee results.

What outside tests have found. Almost every published test of these tools comes from a competitor or a detector company, and most use a single sample.

Undetectable AI

• GPTZero (February 2026). A research paper by GPTZero staff tested 1,000 texts from nine humanizer services. It rated Undetectable AI the only one with “High” ability to beat simpler detectors, but reported that GPTZero itself caught 93.5% of all the humanized texts in its dataset.
• Andy Stapleton (April 2026). In a YouTube test of paid humanizers, the YouTuber ranked Undetectable AI’s Stealth mode second. He reported that Turnitin scored it 0% AI but that Originality.ai was only 59% confident it was original, and said its free Basic mode was “100% detected.” He didn’t say how many texts he tested. His video description has a tracked link to Undetectable AI.
• Originality.ai (August 2026). A single-sample review found Originality.ai still scored the output 100% AI.

Walter Writes

• DEV Community (June 2025). An independent four-sample test found an average human score of about 70%. The writer called it “far too unreliable.”
• Andy Stapleton (April 2026). The same YouTube test listed Walter Writes among the tools whose text was still detected as AI.
• Competitors. Single-sample tests by RewriteAI and Lynote, both of which sell rival humanizers, found GPTZero still scoring its output 100% AI.

Treat every result, ours included, as a snapshot. Detectors retrain often. Turnitin added detection of “AI bypasser” tools for English text in August 2025.

Round 2: Writing quality and meaning

Winner: Undetectable AI

Neither tool’s rewrites were clean, and both got worse when pushed. Undetectable AI’s sentences could turn stiff: in the lab report, “The samples were heated for ten minutes before their mass was recorded” became “Before recording the mass of the samples, they underwent heating for a period of ten minutes.” Walter Writes could soften a claim, turning “Biodiversity helps ecosystems remain stable” into “Biodiversity can be helpful for ecosystems to stay stable.” On retries, Undetectable AI’s More Human setting changed a citation’s punctuation and made the Spanish less idiomatic. Walter Writes’ Enhanced level made several sentences more awkward and changed the lab report’s citation formatting, though it didn’t invent any measurements.

Both tools come with quality warnings, and it’s fair to set them side by side.

Undetectable AI. In a January 2025 paper, Pangram Labs, which makes a competing detector, rated 19 humanizers by hand. It put Undetectable AI in its lowest tier for fluency: “Poorly written text at an elementary school level. Introduces typos.” The paper is almost two years old, and Undetectable AI has released new models since.

Walter Writes. The warning comes from its own help center. It says the Enhanced level “may… introduce minor grammar issues” and “may distort meaning.” Poor output is also the most common complaint in its recent one-star Trustpilot reviews.

Our blind editor ratings decide this round.

Round 3: Settings and languages

Winner: Undetectable AI

The controls are close to identical. Both offer the same five readability levels: High School, University, Doctorate, Journalist and Marketing.

• Purposes: Undetectable AI has nine and Walter Writes ten.
• Strength: both have three escalating modes. Undetectable AI adds a separate strength setting on top: More Readable, Balanced or More Human. That gives you a way to push harder against detectors without jumping straight to the most aggressive mode.

The bigger difference is languages. Undetectable AI lists 55 and says English is its main focus, with “secondary” support for the rest. Walter Writes’ marketing claims “80+,” but its help center names 30, and one outside reviewer found its French output awkward. Walter Writes’ bigger number comes with a caveat. In our test, neither tool got the Spanish sample past a single detector.

Round 4: Price and value

Winner: Walter Writes

This round isn’t close.

On annual billing:

• Undetectable AI: $5.00, $9.50, $15.75 or $21.25 a month.
• Walter Writes: $8, $13 or $26 a month.

Either way, Walter Writes gives you three to four times as many words for similar money.

Undetectable AI’s offsetting perk: a refund of word credits when output gets flagged. It also lets you send longer requests: up to about 1,500 words on any plan, against Walter Writes’ 750 on Starter.

A caveat: Undetectable AI’s pricing page contains several price tables and testing markers in its code, so the prices you see may differ from ours. Check the total at checkout.

Round 5: Free plan and trial

Winner: tie

Each has something the other doesn’t.

Walter Writes offers a 300-word free trial with no card, though it’s limited to the Simple bypass level. Its grammar checker is free.

Undetectable AI offers:

• Free humanizing: 250 words.
• Free tools: its AI detector, with no sign-up, and its paraphraser.
• A trial: three days free on yearly plans. That trial turns into a full yearly charge unless you cancel before it ends, and for most subscribers cancelling means sending an email.

Round 6: Refunds and cancelling

Winner: tie

Both are strict, in different ways.

Walter Writes gives you a short window to get your money back. According to its terms:

• When: only on your first-ever subscription, requested by email within 3 days.
• Usage limit: you must have used 1,500 words or fewer.
• Renewals: “final and non-refundable.”
• Chargebacks: filing one leads to permanent account termination.

Undetectable AI gives you an ongoing guarantee, but in credits, not cash. According to its terms:

• Cash refunds: “Refunds will not be provided unless required by law.”
• Credits: you can get your word credits back within 30 days if a humanized text “provably flags as less than 75% human on a reputable AI detector.”
• Cancelling: by email, except for residents of California and New York, who can cancel in the dashboard.

Billing is the most common complaint about Undetectable AI. Of the 20 most recent one-star reviews on its Trustpilot page when we checked, about 15 described unexpected or renewal charges. Walter Writes’ one-star reviews include refund and cancellation complaints too, though its most common complaint is the quality of its output.

Round 7: Privacy

Winner: tie

Neither company gives the clear answer students need, which is whether your text is used to train its AI.

Undetectable AI

• For it: its detector page says text is “never stored or used to train models,” and its About page says its model is trained on writing from people who consented.
• Against it: its privacy policy dates from March 2023 and doesn’t mention training. It leaves the sentence about server location unfinished (“Our servers are located in.”), and the humanizer keeps a document history.

Walter Writes

• For it: its privacy policy is newer, from September 2025. It mentions self-hosted models, and the company says its SOC 2 Type I controls are verified through Vanta, a compliance platform. We couldn’t check that claim.
• Against it: the policy doesn’t address training either. It says collected data may be used to “develop new services, products, features,” and its Chrome listing’s “never stored” sits awkwardly with the web app’s document history.

If privacy matters to you, delete your document history after each session with either tool.

Round 8: Extra tools and apps

Winner: Undetectable AI

Undetectable AI’s suite is broader:

• Writing tools: an AI essay writer, a “stealth” writer, a paraphraser, a plagiarism checker, an SEO writer and a watermark remover.
• Detectors: for AI text, images, video and deepfakes.
• Chrome extension: 20,000 users.
• For developers: an API from $29 a month and a Zapier integration.

Walter Writes’ strengths are mobile and AI assistants:

• Phone apps: an iPhone app rated 4.6, and an Android app with more than 10,000 downloads.
• Chrome extension: rated 4.8 from 103 ratings.
• Connectors: for Claude, Codex, ChatGPT and Zapier.
• Other writing tools: a paraphraser, a resume rewriter and a free grammar checker.

Both built-in detectors give their own estimate, not results from the detectors your school might use, so treat them as a rough guide.

Round 9: Track record

Winner: Undetectable AI

Undetectable AI has been selling since 2023. It has a large public record:

• Trustpilot: more than 1,000 reviews, averaging 3.5.
• Chrome extension: used by 20,000 people.

Its reviews are polarized, with 51% five stars and 40% one star, and the complaints center on billing, not the product itself.

Walter Writes has been selling since mid-2024. Its record is smaller and leans negative:

• Trustpilot: 63 reviews, averaging 2.9, with 58% one star. The most common complaint is the quality of its output.
• In its favor: the company has replied to 80% of its negative reviews, and its Chrome extension is well rated.

The scorecard

Who should choose Walter Writes

• You’re on a tight budget and humanize a lot. Nothing here comes close on words per dollar.
• You work on your phone. It has iPhone and Android apps; Undetectable AI has no official app.
• You use AI assistants. Its Claude, Codex and ChatGPT connectors are handy.
• You’ll edit every line anyway. If you’re going to rewrite the output yourself, its quality complaints matter less.

Who should choose Undetectable AI

• Getting past detectors is your priority. It passed 13 of our 35 checks, against Walter Writes’ 6.
• You want finer control. The extra strength setting is a useful middle step.
• You write in languages other than English. It lists 55, against the 30 that Walter Writes’ help center names, though neither got our Spanish sample past a detector.
• You’d use a toolkit. An essay writer, a plagiarism checker and more come with the subscription.
• You want an ongoing guarantee. Word credits back for flagged output, within 30 days, is unusual.
• You’ll manage your billing. Note your renewal date, and cancel by email well before any trial ends.

Using either one responsibly

Both companies say one thing in their marketing and another in their policies:

• Undetectable AI: its humanizer page answers “Can I use the AI Humanizer for academic purposes?” with “Absolutely!” Its ethics page, though, calls cheating in school an unacceptable use.
• Walter Writes: it advertises help getting essays past AI checks. Its terms, though, say it “does not support using our technology to circumvent educational AI detection systems when those systems are in place to prevent academic misconduct.”

Go by the policies, and by your school’s:

• Check the AI policy for each course and assignment. Our guide to using AI chatbots to study explains what’s usually allowed.
• Disclose AI help where your instructor asks for it.
• Keep your drafts and version history. Detectors misfire on human writing too: a Stanford study found popular detectors flagged more than half of a set of essays by non-native English speakers as AI-generated.

The verdict

Undetectable AI wins, mainly on detector results. It passed 13 of 35 detector checks to Walter Writes’ 6 and finished ahead on six of the seven detectors; neither got a sample past Pangram. Its rewrites also kept the meaning better, averaging 3.9 out of 5 to Walter Writes’ 3.6. Neither result is impressive, though: Undetectable AI got fewer than four in ten checks past the detectors.

It also gives you a finer strength control, more languages, a broader toolkit and a longer public record. Just manage its billing carefully: note your renewal date, and cancel by email in good time.

Walter Writes is the budget choice, and a strong one on price: three to four times the words for similar money, with phone apps included. Use its 300-word trial to check the output on your own writing before you commit, and keep in mind that you have only three days to ask for a refund.

More humanizer head-to-heads: Hue Write vs. Undetectable AI · WriteHuman vs. Hue Write · Walter Writes vs. Hue Write · WriteHuman vs. Undetectable AI