WriteHuman vs. Undetectable AI: which AI humanizer is better in 2026?

WriteHuman and Undetectable AI are two of the biggest names in AI humanizers, and both launched in 2023. Undetectable AI says it has more than 20 million users and has grown into a suite of writing and detection tools. WriteHuman says it has more than 5 million users and has invested in phone apps and connectors for AI assistants.

Both promise text that reads as human-written and passes AI detectors. We ran both through the same samples and detectors, then compared the things that decide whether you’ll be happy six months in: price, refunds, privacy and reputation.

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 plans at the same price point: Undetectable AI’s 20,000-word plan ($19) and WriteHuman Basic ($20), which uses the same Enhanced model as WriteHuman’s pricier plans. For each sample we chose the settings that matched it:

• Undetectable AI: its top Undetectable mode at University readability, with the matching purpose (Essay, Report, Business Material or Article) and Balanced strength.
• WriteHuman: the Academic tone for the essay, Scientific for the lab report, Professional for the email and Blog for the blog post.

We tested each tool’s first output. Some samples got one retry: More Human strength for Undetectable AI, and WriteHuman’s next variation of the same request. 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 WriteHuman’s homepage says its model was updated for.

• 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 WriteHuman passed 3 (9%). Undetectable AI finished ahead on six of the seven detectors; on Pangram, neither got a single sample through. WriteHuman’s three passes all came on the two most forgiving detectors in our test: ZeroGPT, for the essay and the email, and QuillBot, for the email. Neither tool got our Spanish sample past a single detector, even after a retry. Both needed a retry on two samples, the lab report and the Spanish piece.

Both companies advertise near-perfect results:

• Undetectable AI says its top mode “bypasses 99+% of detectors.”
• WriteHuman’s homepage lists “human scores” after humanizing of 94% to 98% across eight detectors, with no method or date. It also calls itself the “#1 AI humanizer,” based on HumanizerBench, a benchmark WriteHuman itself operates, as the benchmark site discloses.

What outside tests have found. Few of these tests are neutral, so we’ve noted who ran each one.

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.

WriteHuman

• WebSEOTrends (September 2026). A 53-test review by a site that earns referral fees found pass rates of 82% on GPTZero, 51% on Copyleaks, 48% on ZeroGPT and 19% on Originality.ai.
• Phrasly (October 2026). Phrasly, which sells a rival humanizer, found it passed Pangram on 6 of 69 texts.
• Aga Khan University (March 2026). A small peer-reviewed study of two texts found average AI detection fell to about 2% on QuillBot, ZeroGPT and Scribbr.

Our results for WriteHuman were harsher than any of these: it didn’t get a single sample past GPTZero.

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

Undetectable AI held on to the meaning a little better, though its 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.” WriteHuman’s output was the easier read and often natural, as when “Small changes in daily routines can make sustainable habits easier to maintain” became “Making little changes in your everyday routine can help you keep sustainable habits for longer.” Both slipped on retries: Undetectable AI’s changed a citation’s punctuation, and WriteHuman’s reworded a technical term in the lab report. Each also left less idiomatic wording in the Spanish.

Both tools have drawn criticism for quality, and it’s fair to set it 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.

WriteHuman. The criticism is more recent and comes from several directions:

• Its own benchmark gave it 60.0 for keeping meaning, its weakest category.
• Phrasly counted an average of 2.64 factual distortions per output.
• WebSEOTrends found grammar errors in about one in three academic paragraphs.

Most of these sources have a commercial interest, which is why our blind editor ratings decide this round.

Round 3: Settings and languages

Winner: Undetectable AI

Undetectable AI gives you more control. You choose from four kinds of setting:

• Mode: Basic, Stealth or Undetectable.
• Readability level: High School, University, Doctorate, Journalist or Marketing.
• Purpose: nine options, from Essay and Cover Letter to Legal Material.
• Strength: More Readable, Balanced or More Human.

WriteHuman takes a different approach. It offers eight tones: Standard, Professional, Blog, Casual, Creative, Scientific, Technical and Academic. Paid plans also generate several variations of each request, so you can pick the best one: two on Basic, three on Pro and five on Ultra. That’s a genuinely good feature, and one Undetectable AI lacks.

Languages tip it. Undetectable AI lists 55 languages, with English its main focus. WriteHuman claims more than 40. Neither got our Spanish sample past a single detector, though.

Round 4: Price and value

Winner: WriteHuman

The two count usage differently. Undetectable AI sells words. WriteHuman sells requests, each capped at a word limit, so a 200-word paragraph uses up a whole request.

Around $20 a month: WriteHuman. Its Basic plan gives you about twice Undetectable AI’s allowance if your requests run to about 500 words.

Above that: WriteHuman, by more. The gap widens from there.

Very light use: Undetectable AI. If you only need a few thousand words, its $9.99 plan, or $5 a month billed annually, is the cheapest way in.

Annual billing. WriteHuman’s annual plans work out to $12, $19 and $39 a month. Undetectable AI’s run from $5 to $21.25.

What to check on each side:

• WriteHuman raised its prices in late August 2026. Basic had been $18 a month.
• Undetectable AI’s pricing page contains several price tables and testing markers in its code, so the prices you see may differ from ours.
• Undetectable AI’s refund of word credits for flagged output adds some value back.

Round 5: Free plan and trial

Winner: WriteHuman

WriteHuman’s free plan renews every month:

• Humanizing: three requests of up to 250 words each.
• Detection: 10 AI detector checks.
• Phone apps: five free humanizations a month.

The catch is that free users get its basic model, not the Enhanced model they’d be paying for.

Undetectable AI offers:

• Free humanizing: 250 words, once.
• Free tools: its AI detector, with no sign-up, and its paraphraser.
• A trial: three days free on yearly plans. That trial becomes 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: Undetectable AI

Neither is generous, but only one offers anything back.

WriteHuman. Its terms say: “All payments are non-refundable except where the law requires a refund.”

• No partial refunds: nothing back for a part-used period or for unused words.
• Cancelling: takes effect at the end of the billing period. App subscriptions have to be cancelled through Apple or Google.

Undetectable AI. Its terms also rule out cash refunds “unless required by law.”

• Credits: they do return word credits within 30 days if a humanized text “provably flags as less than 75% human on a reputable AI detector.” That’s a real, if limited, guarantee.
• Cancelling: most subscribers have to cancel by email. Residents of California and New York can cancel in the dashboard.

Both draw billing complaints on Trustpilot:

• Undetectable AI: of the 20 most recent one-star reviews when we checked, about 15 described unexpected or renewal charges.
• WriteHuman: of its 20 most recent one-star reviews, six described a refused refund and six unexpected charges.

Round 7: Privacy

Winner: Undetectable AI

Neither privacy policy is a model, but only one says it trains on your writing.

WriteHuman’s privacy policy, updated in September 2026:

• Training: it says WriteHuman uses the text you submit to train its models, with “no setting to opt out.”
• No removal: “Content used to train a model cannot be removed from it.”
• Your rights: its terms give WriteHuman an irrevocable license to your content that survives deleting your account.
• Sharing: its processors include OpenAI, Google’s Gemini API and the detector company GPTZero, and the policy says samples of humanized text may be sent to GPTZero.
• The exception: text sent through its API or MCP connector isn’t stored or used for training.

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 you’ll want to clear.

Neither lists a security certification. For a student pasting in an unpublished essay, though, the difference is clear.

Round 8: Extra tools and apps

Winner: tie

They’ve built in different directions, and which is better depends on where you work.

Undetectable AI suits the desk:

• Writing tools: an AI essay writer, a “stealth” writer, a paraphraser, a plagiarism checker and an SEO writer.
• Detectors: for AI text, images, video and deepfakes.
• Chrome extension: 20,000 users and a 4.7-star rating.
• For developers: an API from $29 a month and a Zapier integration.

WriteHuman suits the phone:

• Phone apps: its Android app has more than 100,000 downloads and a 4.8-star rating from about 14,600 reviews, and its iPhone app is rated 4.8 from 229 ratings.
• Detectors: a free AI text detector, plus detectors for AI images and video.
• AI assistants: an MCP connector, on Pro and Ultra.
• For developers: a separate API, from $29 a month.
• Chrome extension: its weak spot, with 1,000 users and a 3.5-star rating.

Round 9: Track record

Winner: WriteHuman

Both have been around since 2023, and Undetectable AI is the bigger of the two by its own figures. On ratings, though, WriteHuman comes out ahead:

WriteHuman’s app ratings are strong too. One caveat: many of its recent five-star reviews are short one-liners, and only one of the 20 newest was marked as verified.

The scorecard

Who should choose WriteHuman

• You mostly work on your phone. Its apps are among the best-rated in the category.
• You humanize a lot. From about $20 a month, it gives you more words for your money.
• You like choosing between versions. Several variations per request make it easy to pick the one that sounds most like you.
• Your text isn’t sensitive. Its training policy matters less for marketing copy than for a thesis chapter. If privacy matters, its API and MCP connector aren’t used for training.

Who should choose Undetectable AI

• Getting past detectors is your priority. It passed 13 of our 35 checks, against WriteHuman’s 3.
• You’re pasting your own unpublished work. Its own pages say it doesn’t train on your text. WriteHuman’s policy says it does.
• You want fine control. Readability level, purpose and strength let you tune each piece to its reader.
• You’d use the flagged-output guarantee. Word credits back for flagged text, within 30 days, is more than WriteHuman offers.
• You’d use a toolkit. An essay writer, a plagiarism checker and more come with the subscription.
• You’ll manage your billing. Note your renewal date, and cancel by email well before any trial ends.

Using either one responsibly

Both companies’ policies are clear that academic dishonesty is your responsibility:

• WriteHuman’s terms prohibit using the service to “engage in academic dishonesty.”
• Undetectable AI’s ethics page calls cheating in school an unacceptable use, even though its humanizer page answers “Can I use the AI Humanizer for academic purposes?” with “Absolutely!”

Whichever you use:

• 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 WriteHuman’s 3 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 WriteHuman’s 3.6. Neither result is impressive, though: Undetectable AI got fewer than four in ten checks past the detectors.

Beyond the tests, the biggest difference is privacy. WriteHuman says it trains on what you paste in, with no way out. Undetectable AI says it doesn’t. Add finer controls and a refund of credits when output gets flagged, and it’s the safer home for coursework. Just keep on top of its billing.

WriteHuman is the better-liked product, and it earns that. Its phone apps are excellent, its free plan renews monthly, and it gives you more for your money. For non-sensitive writing on the go, it’s a strong pick.

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