> We tested SupWriter and Undetectable AI on the same detectors — bypass rates, meaning preservation, 5 languages, and real 2026 pricing. Honest head-to-head. - **Published**: 2026-07-30 - **Category**: Tool Reviews - **URL**: https://supwriter.com/blog/supwriter-vs-undetectable-ai --- # SupWriter vs Undetectable AI: Head-to-Head Test Results (2026) Undetectable AI is the most recognized name in the humanizer market. SupWriter is ours. Here is how they actually compare when you put both through the same detectors. Let's get the bias out of the way first: we built SupWriter, so read everything below with appropriate skepticism. What we can promise is that the numbers here are the same ones we have already published elsewhere on this blog — same sample sets, same detectors, same scoring rules — and that we have not quietly rounded Undetectable AI down to flatter ourselves. There are places where they genuinely beat us, and we say so in plain language. If you only have thirty seconds: SupWriter wins on bypass rate, academic register, speed, and non-English quality. Undetectable AI wins on brand trust, breadth of tooling, and — depending on which tier you buy — sometimes on price. Which of those matters more depends entirely on what you are submitting and where. ## Quick Verdict | Metric | Undetectable AI | SupWriter | |---|:---:|:---:| | Overall bypass rate | ~85% | 99%+ (500-sample, five detectors) | | Turnitin (academic set) | 88% | 92% | | GPTZero (academic set) | 86% | 94% | | Originality.ai (academic set) | 82% | 88% | | Academic-set average | 85.3% | 91.3% | | Academic tone (scholarly register) | 7.15/10 | 8.95/10 | | Processing speed | 15-30 sec per pass | 3-5 sec per 1,000 words | | Languages supported | 50+ | 100+ | | Entry price | ~$9.99/mo for 10,000 words | $9.99/mo for 30,000 words | | Free tier | Free trial, ~250 words | 300 words, no account needed | | Extra tools | Essay writer, SEO writer, image detector, multi-detector scan | Humanizer, detector, grammar, paraphraser | A note on why there is no Copyleaks row, since a missing detector in a comparison table usually means somebody is hiding something. The academic study behind that block ran three detectors — Turnitin, GPTZero, and Originality.ai — so neither tool has an academic-set Copyleaks figure. SupWriter's 99.4% against Copyleaks comes from the separate 500-sample run, a different sample set under a stricter scoring rule, so it is not comparable to anything in the academic rows and we have not lined it up as if it were. Same reason the overall row sits on its own: ~85% and 99%+ are answering slightly different questions. ## Bypass Rates, Detector by Detector The academic run is the one worth studying, because it is the context where being flagged has actual consequences. Across academic papers, Undetectable AI averaged **85.3%** — 88% against Turnitin, 86% against GPTZero, 82% against Originality.ai. That is a legitimately good result. It is better than most of the field, and considerably better than paraphrasers being misused as humanizers. If somebody tells you Undetectable AI does not work, they are wrong. SupWriter averaged **91.3%** on the same academic set, and 99%+ on our broader 500-sample run across five detectors, where a text only counted as a pass if every single detector cleared it. Six percentage points sounds like a rounding error until you convert it into submissions. At 85%, roughly one paper in seven still trips a detector. At 91-99%, depending on content type, you are somewhere between one in eleven and one in a hundred. If you submit twenty assignments a semester, that difference is the gap between "probably fine" and "statistically going to happen to me at least once." The pattern holds against newer detection tooling too. When we tested Turnitin's counter-bypass feature, it flagged 14% of SupWriter-processed text versus 41% of text from other humanizers in the same bucket. We wrote up that whole experiment in our [Turnitin 2026 bypasser detection analysis](/blog/turnitin-2026-bypasser-detection) if you want the methodology. One more honest caveat that applies to both tools: no humanizer is at 100%, nobody's is, and any vendor claiming otherwise is selling you certainty they cannot deliver. Run your output through an [AI detector](/ai-detector) before you submit anything that matters. That is not a sales pitch, it is just basic hygiene. ## Academic Register: The Metric Nobody Markets Bypass rate is the number every humanizer puts on its homepage. Whether the output still sounds like academic writing is the one that decides whether it is usable. Undetectable AI scored **7.15/10** for scholarly register on our academic evaluator panel, where independent readers rated blind outputs, and it was weakest on humanities writing at 6.8. SupWriter scored **8.95/10** on the same panel. A 7.15 is not a disaster. It means the output usually still reads as academic prose. What our readers marked down was consistent: hedged claims hardening into absolute ones, technical terms getting swapped for near-synonyms that are not actually synonyms in that field, and the occasional restructured sentence that changes which clause is doing the work. In a marketing blog post, none of that matters much. In a literature review where "suggests a correlation" becomes "demonstrates," it matters a great deal. The same academic study looked at what happens to references, and that is where the widest gap showed up. Undetectable AI left 61% of citations fully intact, with major breakage in 17% of them — roughly four references to repair by hand in a 25-source paper. SupWriter's figure on the same measure was 94%. There is also a formatting wrinkle worth knowing about: Undetectable AI strips formatting during humanization. Bold, headers, bullets, and links come out flattened, so if you are running a structured document through it, budget time for putting the structure back. ## Before and After: What the Output Actually Looks Like Numbers are abstract. Here is a paragraph of standard ChatGPT academic filler, and what each tool did with it. **The original AI text:** > Remote work has fundamentally transformed the modern workplace in numerous significant ways. Studies suggest that employees who work remotely may experience increased productivity, although results vary considerably across industries and roles. Organizations must therefore carefully consider a variety of factors when implementing remote work policies. **Undetectable AI's rewrite:** > Remote employment has thoroughly reshaped the contemporary workplace across many meaningful dimensions. Research demonstrates that staff members working remotely experience heightened productivity, though outcomes differ substantially between sectors and positions. Companies should therefore thoughtfully weigh numerous considerations while establishing remote work policies. **SupWriter's rewrite:** > Remote work has changed the workplace, and not in one tidy direction. Some studies find remote employees get more done. Others find the opposite, and the split usually tracks with the industry and the specific role rather than with remote work itself. So policy decisions have to start from what the job actually involves. Look at what happened to the hedge in the second sentence. The original said studies "suggest" that productivity "may" increase. Undetectable AI's version says research "demonstrates" that staff "experience" heightened productivity. That is a real claim strengthening, and in an assessed paper it is the kind of thing that gets a comment in the margin. The Undetectable AI output is also doing something detectors have gotten good at spotting: register inflation. Work becomes employment, modern becomes contemporary, many becomes numerous. Every word gets one notch fancier while the sentence rhythm stays identical. Human writers do not upgrade every noun at once, and they do not write three sentences of matching length in a row. ## Languages: Where the Gap Gets Wide This is the clearest separation between the two tools, and it is the reason a lot of our non-English users switched. We ran a 300-sample multilingual test across five languages. Bypass was measured by detector consensus — a text counted as flagged if two or more of Turnitin, GPTZero, Originality.ai, and Copyleaks agreed on it. Native speakers rated meaning preservation and grammar only: | Language | Undetectable AI bypass | SupWriter bypass | Undetectable AI grammar | SupWriter grammar | |---|:---:|:---:|:---:|:---:| | Spanish | 72% | 94% | 3.8/5 | 4.7/5 | | French | 65% | 91% | 3.6/5 | 4.6/5 | | German | 58% | 89% | 3.2/5 | 4.5/5 | | Chinese | 45% | 88% | 2.8/5 | 4.4/5 | | Arabic | 41% | 86% | 2.5/5 | 4.3/5 | Spanish is close enough to be a fair fight. By the time you reach Arabic and Chinese, it is not a fight at all. Undetectable AI supports 50+ languages and its Spanish output is solid, but a 3.2 in German and sub-3.0 scores in Chinese and Arabic mean a native speaker will notice something is off — wrong case endings in German, awkward segmentation in Chinese, output that reads like it took a detour through English and back. SupWriter supports 100+ languages, including Hindi and other Devanagari-script languages that most humanizers handle badly. We should be straight with you, though: Hindi was not part of that 300-sample panel, so we do not have a published Hindi bypass number to show you. What we have is the architectural reason the tested languages held up — language-specific processing rather than a translate-humanize-retranslate pipeline — and a lot of user reports. Treat the five numbers above as evidence and Hindi as a reasonable extrapolation, not a measurement. Our full writeup on this is in [AI humanizer for non-English content](/blog/ai-humanizer-for-non-english-content), including why detectors themselves misfire on non-English text in the first place. ## Speed Undetectable AI runs roughly 15-30 seconds per pass. SupWriter runs 3-5 seconds per 1,000 words, and stays flat as documents get longer — a 300-word email and a 2,500-word essay take about the same time per thousand words. Is speed the deciding factor? Almost never. But if you are iterating — humanize, check, adjust tone, humanize again — the difference between a 5-second loop and a 20-second loop changes how many passes you are willing to try before deadline. ## Pricing and Free Tiers Undetectable AI's pricing has moved around, so check their page before you commit. As of mid-2026 the entry tier is around $9.99/month for 10,000 words, 20,000 words runs $19.00, and 50,000 words runs $42.50. Annual billing roughly halves all of those, which puts the entry tier near $5/month. Credits generally do not roll over. SupWriter is $9.99/month for 30,000 words, which works out to about $0.33 per 1,000 words. Here is the fair version of the comparison, because a straight sticker-price fight is misleading. At the entry tier, SupWriter gives you three times the words for the same money — $0.33 per 1,000 versus roughly $1.00. Their bigger tiers do not close that gap: 50,000 words at $42.50 is $0.85 per 1,000, still more than double our rate. What does close it is annual billing. At roughly $5/month for 10,000 words, the annual entry plan works out to about $0.50 per 1,000, and that is genuinely competitive if 10,000 words a month covers your needs. Where the gap reopens is when you adjust for failure rate. Words that come back flagged are words you pay for twice, since you either re-run them or rewrite them by hand. At ~85%, roughly 1,500 of every 10,000 words need a second pass. That is the hidden line item. Our [AI humanizer pricing comparison](/blog/ai-humanizer-pricing-comparison-2026) works through that math across eight tools. On free tiers: Undetectable AI offers a trial of roughly 250 words. SupWriter's [free humanizer](/free-humanizer) gives you 300 words with no account and no card. Both are enough to form an opinion, which is more than several competitors offer. ## Where Undetectable AI Genuinely Wins We are not going to pretend this is a one-sided product. **Human Typer.** This is their most distinctive feature and nobody else ships it. It replays your text into a document as timed keystrokes rather than a paste, which answers a problem the rest of us do not touch at all: Google Docs and most LMS platforms keep a revision history, and a 2,000-word paste event at 11:58pm is its own kind of evidence regardless of how the text scores. If your institution reads revision histories, that feature is doing something no bypass rate can. **Breadth of tooling.** Undetectable AI is a suite, not a single tool. AI essay writer, SEO writer, job application bot, AI image detector, an English-to-Spanish translator. Their paid tiers also include the full suite and API access rather than feature-gating the extras behind a higher plan, which is not how most of this market prices. If you want one subscription covering generation and humanization, that consolidation is worth real money. **Multi-detector scanning.** Their built-in checker runs your output against several detectors in one place before you copy it out. It is a genuinely good workflow feature and we do not currently match it. **Brand and longevity.** They have been in this market since 2023 and they are not going anywhere. If you are buying tooling for a team and need to justify the vendor to someone else, name recognition is a legitimate factor, not a vanity one. **Marketing content.** For blog posts, social copy, and product descriptions where a flag costs you nothing, 85% is plenty and the register-inflation problem barely registers. ## Who Should Pick Which **Pick SupWriter if:** you are submitting through Turnitin or another institutional detector, you write in a language other than English, scholarly register and intact citations matter more than convenience, or you process enough volume that the per-word rate is a real cost. **Pick Undetectable AI if:** you want the whole content pipeline in one subscription, you value multi-detector checking in the same window, you are producing low-stakes marketing content, or 10,000 words a month on the annual entry plan genuinely covers you. If you are weighing other options too, our roundups of the [best AI humanizer tools](/blog/best-ai-humanizer-tools) and [best AI humanizer for academic papers](/blog/best-ai-humanizer-for-academic-papers) cover the wider field, and we keep a dedicated [Undetectable AI alternative](/undetectable-ai-alternative) page. ## Just Run the Test Yourself Honestly, this is the part we would push hardest. Generate a paragraph with ChatGPT. Run it through Undetectable AI's trial. Run the identical text through SupWriter's [AI humanizer](/ai-humanizer). Put both outputs into GPTZero or Originality.ai, then read them side by side and ask which one you would actually submit under your own name. That takes about five minutes and it beats trusting a comparison written by one of the two companies involved. Including this one. --- *Try it on your own text — [300 words free, no credit card required.](/ai-humanizer)* --- Source: https://supwriter.com/blog/supwriter-vs-undetectable-ai