Undetectable AI costs less on a yearly plan and has more extras, like a Chrome extension, an API and 55 languages. Lumi is better value for heavy use: $49.90 a month buys unlimited words, with a detector, paraphraser, grammar and plagiarism checker included.
300 free words when you sign up · Facts checked October 18, 2026
List prices in US dollars before tax, as each company's own pages showed them on October 18, 2026. Where a page doesn't say, we write "Not stated". Numbers in brackets link to the sources at the bottom.
| Feature | UsLumi Humanizer | Undetectable AI |
|---|---|---|
| Cheapest plan, monthly billing | $9.90/mo[1] Starter, 10,000 words a month | $9.99/mo[3] 10,000 words a month |
| Cheapest plan, yearly billing | $6.00/mo[1] $72.00 billed yearly | $5.00/mo[3] $60 billed yearly |
| What about $50 a month buys | Unlimited words for $49.90/mo[1] Up to 3,000 words per request | 50,000 words for $42.50/mo[3] A slider goes up to 380,000 words for $209/mo |
| Words per month, by plan | 10,000 / 100,000 / Unlimited[1] Starter / Pro / Unlimited | 10,000 to 380,000[3] Plans are word tiers chosen on a slider |
| Words per request, by plan | 500 / 1,000 / 3,000[1] Starter / Pro / Unlimited | Not stated |
| Languages | English only | 55 listed[4] English is the main focus; the others are secondary |
| Free option | 300 free words Added to your account when you sign up | Free basic model, plus a 250-word trial[4] The site says the basic model may be flagged. The trial needs an account. |
| Refunds | No refunds[2] Cancel anytime; you keep access until the end of the paid period | No refunds unless the law requires[5] Credits back if output scores under 75% human on a reputable detector, claimed within 30 days |
| Also included | AI detector, paraphraser, grammar checker, plagiarism checker[1] On every plan. No Chrome extension or public API. | AI detector, paraphraser, Chrome extension, API[3][4][6][7] |
Undetectable AI
Lumi Humanizer
Pick Undetectable AI if
Pick Lumi if
Both tools do the same core job: rewriting AI-assisted text so it reads naturally. Undetectable AI has the longer feature list and more languages. Lumi is the simpler and cheaper choice once you rewrite more than about 50,000 words a month. Results depend on your text, so try each on a real draft before paying.
Quick answers about Lumi Humanizer vs Undetectable AI.
On monthly billing the entry plans cost about the same: $9.90 for Lumi and $9.99 for Undetectable AI, both for 10,000 words. On yearly billing Undetectable AI is cheaper ($5.00 against $6.00 a month). For heavy use Lumi is cheaper, with unlimited words for $49.90 a month.
Lumi gives 300 free words when you sign up. Undetectable AI has a free basic model and a 250-word trial of its main model, which needs an account.
Lumi does not offer refunds, but you can cancel anytime and keep access until the end of the paid period. Undetectable AI's Terms say no refunds unless the law requires one, though credits can come back if output scores under 75% human on a reputable detector, claimed within 30 days.
Yes. Lumi includes its AI detector on every plan, and Undetectable AI lists unlimited AI detection on every plan.
Undetectable AI lists 55 languages, with English as its main focus. Lumi works in English only, so pick Undetectable AI if you write in other languages.
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