Best for heavy use on a budget
Lumi Humanizer
Unlimited words for $49.90 a month, and the entry plan starts at $9.90. Detector, paraphraser, grammar and plagiarism checks are included. English only, no refunds, and no app or extension.
Undetectable AI alternatives
The main alternatives to Undetectable AI are Walter Writes, StealthGPT, QuillBot, Grammarly and WriteHuman, plus Lumi, which made this page. Here is what each costs and includes, from their own pages.
300 free words when you sign up · Facts checked October 18, 2026
Side by side
The facts, with sources
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 | Walter Writes AI | StealthGPT | QuillBot | Grammarly | WriteHuman |
|---|---|---|---|---|---|---|
| Cheapest plan, monthly billing | $9.90/mo[1] Starter, 10,000 words a month | $12/mo[3] Starter, 30,000 words a month | $29.99/mo[6] Pro, 50,000 words a month | $19.95/mo[8] Premium | $30/mo[13] Pro | $20/mo[16] Basic |
| Cheapest plan, yearly billing | $6.00/mo[1] $72.00 billed yearly | $8/mo[3] $96 billed yearly | $24.99/mo[6] Pro, billed yearly | $8.33/mo[8] $99.95 billed yearly | $12/mo[13] $144 billed yearly | $12/mo[16] $144 billed yearly |
| What about $50 a month buys | Unlimited words for $49.90/mo[1] Up to 3,000 words per request | 200,000 words for $47/mo[3] Elite plan | 200,000 words for $49.99/mo[6] Max plan, 2,000 words per request | Premium, $19.95/mo[8][9] No word or usage limit | Pro, $30/mo[13] Humanizer word limits not stated | Pro, $29/mo[16] 200 requests of up to 1,200 words. Ultra is $59. |
| Words per month, by plan | 10,000 / 100,000 / Unlimited[1] Starter / Pro / Unlimited | 30,000 / 70,000 / 200,000 / 500,000[3] Starter / Pro / Elite / Teams | 50,000 / 200,000 / 1,000,000+[6] Pro / Max / Enterprise. Weekly plans also exist. | No word or usage limit on Premium[9] | Not stated | Counted in requests[16] 80 / 200 / unlimited requests |
| Words per request, by plan | 500 / 1,000 / 3,000[1] Starter / Pro / Unlimited | 750 / 1,500 / 2,000 / 2,000[3] An older help article lists lower limits | 1,000 / 2,000 / 10,000+[6] Pro / Max / Enterprise | Not stated | Not stated | 600 / 1,200 / 3,000[16] Basic / Pro / Ultra |
| Languages | English only | 80+[3] | 100+[6] The same page also says "50+" and "all languages" | English, Spanish, German, French, Portuguese[10] For the humanizer | 6[14] English, Spanish, French, German, Portuguese, Italian | 40+[17] Its FAQ names 45 |
| Free option | 300 free words Added to your account when you sign up | 300-word trial[4] Plus 3 days of AI detector access. Email sign-up, no card. | $1 for 3 days[6] Paid trial of Pro or Max | Free humanizer with word limits[9][11] QuillBot's blog says 100 words at a time | Free basic humanizer[14] A free account adds preset voices | 3 free requests a month[16] Up to 250 words each, no sign-up |
| Refunds | No refunds[2] Cancel anytime; you keep access until the end of the paid period | First subscription only[5] Within 3 days and with 1,500 words or fewer used. Renewals are not refunded. | Non-refundable, with a "detected?" policy[7] Money back for the current cycle with a screenshot from an accepted detector | Only where the law requires[12] 14-day withdrawal right in the EEA and UK | Only where the law requires[15] Cancel anytime | Only where the law requires[18] |
| Also included | AI detector, paraphraser, grammar checker, plagiarism checker[1] On every plan. No Chrome extension or public API. | AI detector, MCP access, API platform[3] Also lists "ChatGPT watermark removal" | AI detector, iOS app, Chrome extension, MCP[6] API on the Enterprise plan | Paraphraser, grammar checker, AI detector, plagiarism checker[9] Plus a Chrome extension and desktop and mobile apps | Grammar checker, AI detector, paraphraser, browser extension[14] Says its humanizer is not meant to bypass AI detectors | AI detector, Chrome extension, API[16][19][20] |
Best fit
Which alternative fits you
Best for many languages and a first-purchase refund
Walter Writes AI
Lists 80+ languages and gives 30,000 words on its $12 plan. It refunds a first subscription within 3 days if you used 1,500 words or fewer.
Best for an app and weekly plans
StealthGPT
Has an iOS app, a Chrome extension, weekly billing and a $1 three-day trial. Monthly plans start at $29.99.
Best for paraphrasing first, humanizing second
QuillBot
Its free humanizer has word limits (100 words at a time, according to its blog), and Premium has no word or usage limit. Grammar, AI detection and plagiarism checks are part of the same suite.
Best for people who already use Grammarly
Grammarly
Has a free basic humanizer. Grammarly says the tool is not meant to bypass AI detectors.
Best for trying without an account
WriteHuman
Gives 3 free requests a month of up to 250 words each, with no sign-up. Paid plans count requests, not words.
Our take
There is no single best alternative. If you rewrite a lot, compare what about $50 a month buys. If you write in many languages, check each tool's language list. And because no tool can promise a result on every detector, try the free options on your own text first.
Frequently asked questions
Quick answers about Undetectable AI alternatives.
What is the cheapest Undetectable AI alternative?
On monthly billing, Lumi has the cheapest paid plan here at $9.90, and also the cheapest yearly price at $6.00 a month. Grammarly, QuillBot and WriteHuman also have free options with limits.
Which alternatives have a free plan or trial?
WriteHuman gives 3 free requests a month with no sign-up. Grammarly has a free basic humanizer. QuillBot's free humanizer takes 100 words at a time. Lumi gives 300 free words on sign-up, Walter Writes a 300-word trial, and StealthGPT a $1 three-day trial.
Do any of them offer refunds?
Walter Writes refunds a first subscription within 3 days if you used 1,500 words or fewer. StealthGPT has a money-back policy if you can show your text was flagged. QuillBot, Grammarly and WriteHuman refund only where the law requires. Lumi does not offer refunds.
Can any of these tools guarantee passing AI detectors?
No. Detectors change often and results depend on the text. Grammarly says its humanizer is not meant to bypass AI detectors. Treat any guarantee with caution and test on your own writing.
Still have questions? Visit our help center or read our blog guides.
Sources
- [1] Lumi Humanizer: Pricing. Checked October 18, 2026.
- [2] Lumi Humanizer: Terms of Service. Checked October 18, 2026.
- [3] Walter Writes AI: Pricing. Checked October 18, 2026.
- [4] Walter Writes AI: How do I use the free trial?. Checked October 18, 2026.
- [5] Walter Writes AI: Can I get a refund?. Checked October 18, 2026.
- [6] StealthGPT: Pricing. Checked October 18, 2026.
- [7] StealthGPT: Terms of Service. Checked October 18, 2026.
- [8] QuillBot: How much is QuillBot Premium? (QuillBot blog, updated February 2026). Checked October 18, 2026.
- [9] QuillBot: AI Humanizer. Checked October 18, 2026.
- [10] QuillBot: Humanizer languages (help center) (the page blocked our check, so we used a search-engine copy). Checked October 18, 2026.
- [11] QuillBot: Best AI humanizer (QuillBot blog). Checked October 18, 2026.
- [12] QuillBot: Refund policy (help center) (the page blocked our check, so we used a search-engine copy). Checked October 18, 2026.
- [13] Grammarly: Plans (prices from the plan data in the page). Checked October 18, 2026.
- [14] Grammarly: AI Humanizer. Checked October 18, 2026.
- [15] Grammarly: Can I get a refund?. Checked October 18, 2026.
- [16] WriteHuman: Pricing. Checked October 18, 2026.
- [17] WriteHuman: Homepage FAQ. Checked October 18, 2026.
- [18] WriteHuman: Terms. Checked October 18, 2026.
- [19] WriteHuman: Chrome extension. Checked October 18, 2026.
- [20] WriteHuman: API. Checked October 18, 2026.
Plans change often. If something here is out of date, email contact@lumihumanizer.com and we'll fix it.