Grubby AI Review: I Read the Guarantee and the Terms (2026)

Grubby AI's pricing page carries a green banner: "Turnitin Guarantee: Grubby is the only humanizer that guarantees our text bypasses Turnitin's AI detector." Its guarantee page says "No fine print, no runaround. If it doesn't pass, you don't pay." Its terms and conditions say "All purchases are non-refundable."

All three of those sentences were on the site on 3 October 2026, about four clicks apart.

I was going to use this tool in a similar way to how I used Grammarly's humanizer and Walter Writes: by pasting a 255-word sample into the tool, scoring the output and publishing those numbers. However, this is not possible with Grubby. There is no logged-out version of the tool. Every button on the site, including the nav item labelled "AI Humanizer", takes users to a sign-up form. I did not register. Instead, I read the paperwork, which took about forty minutes to complete and provided me with a clearer picture of what the tool does than a detector score would have.

What Grubby AI sells, in its own words

The homepage headline is "Humanize AI text & bypass AI detectors", under a subhead calling it "the fastest, most affordable, and least detectable AI humanizer, guaranteed to outperform any competitor". The footer on every page reads "Make your AI text 100% undetectable with a trusted AI bypasser." A band near the top says "We beat every AI detector" above nine logos.

The audience is not implied, it is stated. "Over 1.6 million students have used the Grubby AI humanizer tool," says the homepage. "About 14,000 students use Grubby AI every week to submit papers with confidence," says the guarantee page.

The evidence offered for "we beat every AI detector" is a tab strip with seven tabs: GPTZero, Originality.ai, ZeroGPT, Turnitin, Winston AI, Content at Scale, Copyleaks. Each tab shows a screenshot of a product test result with the caption "Bypass GPTZero, test sample from GrubbyAI." These are pictures supplied by the vendor of the product that they performed the test with. Every humanizer does this, even the ones that I rate well, and it's worth remembering what this is.

The site is operated by Study Solutions A16 LLC, and GRUBBY.AI is a registered service mark. The tool handles English only.

The guarantee page, and the link underneath it

The guarantee is the reason this product ranks. It is specific and it is unusual: "If our humanized text gets flagged by Turnitin as AI-generated, we'll refund the cost of your subscription."

Three things about that page. The first is the number holding it up: "99.8% Bypass Rate — Across thousands of Academic mode submissions". There is no date, no sample size beyond "thousands" and no description of how a pass was counted. The second is the scope, which moves as you read down. The headline says Turnitin. Step 03 is titled "If It Gets Detected" and its body says "In the rare event that your Grubby-humanized text gets flagged by an AI detector" — any detector, which is a far bigger promise than the headline makes, sitting two inches below it.

The third is the link. The page says "Three simple steps. No fine print, no runaround," and its own footer offers a Refund Policy link pointing at grubby.ai/refund-policy. That URL returns HTTP 200 and an empty page. I checked it in a browser and fetched the raw HTML: 327 characters of visible text, all of which was the website's own header and footer. There is no refund policy published at the address provided by the website.

What the terms actually say about refunds

The terms and conditions are published, long and recently maintained; they cite the California Automatic Renewal Law and New York General Business Law §§ 527-a and 527-b by name, which is more care than most tools in this category take. That makes what they say about the guarantee harder to read as an oversight.

Read §8.5 and §10 together and the position is that the subscription is non-refundable, the two exceptions to this are the case of price rises for the subscription service and the section of the contract that promises the guarantee of the subscription service is silent. The guarantee may well be honoured in practice — and the company that publishes this contract usually honours its guarantees. However, on the documents as published this is a goodwill policy and not a contract term.

The clause that prohibits what the homepage advertises

Section 6.2 is worth quoting in full context. It lists examples of prohibited use: "submitting copyrighted or plagiarized content, using the Services for cheating or academic misconduct, spreading misinformation, harassing or defaming others, or attempting to gain unauthorized access to Grubby.ai systems or user accounts."

The homepage counts its users in students. The guarantee page counts them in submitted papers and offers an "Academic mode" that is "specifically engineered to counter Turnitin's detection patterns". Turnitin is a tool used by educational institutions to enforce their academic integrity policies. Using this mode to pass Turnitin and then submitting the result is doing the thing that §6.2 prohibits and under a plan that was sold to those people.

In this category of vendors, most of the time they will hedge their bets by selling to "writers" and "marketers" and letting the students find them. Grubby does not hedge in the marketing and then prohibits the use in the contract, leaving the user with the risk that the homepage says does not exist.

AutoTyper is not a humanizer

Section 5 of the terms describes a feature the marketing barely mentions. AutoTyper connects to your Google account, and types text you give it into a Google Doc you select, "using simulated typing patterns over a duration you choose". You pick a realism level from "Subtle, Natural, and Heavy", which the terms say "are designed to make AutoTyper-entered text resemble human typing". Sessions run on Grubby's servers rather than in your browser, can last "several hours, days, or up to one week", and Grubby "retains your Google authorization tokens" for as long as a session is live.

No classifier reads typing rhythm. The thing that reads typing rhythm is Google Docs version history. which some instructors now check when a submission looks wrong. AutoTyper is aimed at that. AutoTyper is a different product from a text rewriter. It's the feature that the terms disclaim hardest. §5.8 puts the responsibility for "any consequences" onto the user and disclaims any warranty of third party acceptance. Every paid tier includes AutoTyper, from 5,000 words a month on Essential to unlimited on Enterprise.

What Grubby AI costs

These prices are the default shown on the pricing page for the annual subscription. The free plan allows 300 words per month but requires an account to use.

The asterisk is theirs and the footnote under the grid reads: "Unlimited plan: subject to a 30,000 word/day fair-use limit." The 500-word input cap on Essential matters more than the monthly allowance for anyone pasting an essay — a 2,000-word paper goes through in four pieces and rewriters are at their worst across boundaries they cannot see.

Every tier lists "100% human score content" and "Bypass all detectors" as features of their product, yet the terms for these products decline to make such promises.

Is Grubby AI a scam?

No, and that is the wrong question. A scam does not publish a terms page citing New York's automatic-renewal statute by section number and does not build a cancellation flow it describes as "at least as easy as signup". What Grubby has is a marketing layer making promises its legal layer withdraws, which is normal in this category and unusually easy to document here because the two layers are three clicks apart.

The practical reading: consider the Turnitin guarantee as a refund request you might be able to win on goodwill rather than enforce. Take the 99.8% figure with a grain of salt; you can't verify it anywhere on the site. If something goes wrong with your submissions, you're the one responsible; §5.8 and §6.2 say as much.

Our own position is not different in kind, so I will state it. RewriteAI's humanizer has no guarantee of this sort and I will not write one, because no tool can promise what a detector will say next month. When I last put the output of our own humanizer in front of an independent detector on 25 September, it returned a 99.6% score for AI on generic essay filler, which I published at the time. Rewriting changes words. Detectors mostly score structure. Any humanizer that tells you otherwise is selling the same thing Grubby is selling, with or without the paperwork. If you want a tool for this category, compare them on what they will put in a contract.

The short version

Grubby AI is a real product with a guarantee page and a contract that does not back it. The guarantee page says "no fine print" and links to an empty refund-policy page. The terms of service say that all purchases are non-refundable and route the guarantee to a section that says nothing about refunds. Section 6.2 prohibits academic misconduct in a product that will be used by 1.6 million students to pass Turnitin. The most consequential product is AutoTyper, which simulates human typing into Google Docs for up to a week at a time. Prices are low and the free tier has 300 words. None of this is unusual for the category — it's just written down.

If you want the longer treatment:

• Alternatives to Grubby, including what each one will and will not promise
• How Turnitin AI detection actually works, which is what Academic mode claims to counter
• Walter Writes AI review, where I could run the sample and did
• How to judge an AI humanizer without trusting anyone's screenshots
• Are AI detectors accurate? — every published number in one table