Grubby AI Humanizer Review

Grubby AI Humanizer (grubby.ai) is a subscription based AI Humanizer with a small free plan around 300 words/month. No credit card required. It has different modes that are named after detectors such as Turnitin and GPTZero.

Detectors showed mixed results, so we scored it on the writing itself.

In this Grubby AI Humanizer review, we are scoring how it performs on your writing and not just getting a lower score on a detector. We wrote 3 different pieces (schoolwork, marketing piece, and an article packed with facts). Scored each for meaning retained, facts retained, readability, and edits.

Then we looked at cost, money-back guarantee, safety, and other AI humanizers.

We tested this in November 2026. Also checked the pricing page and terms. Phrasly will score this, as Phrasly makes a competing AI Humanizer and will name all categories that Grubby won.

Grubby AI Humanizer at a Glance

Is Grubby free? Well, it's free for trial purposes. You can get about 300 words a month with no credit card. Not quite enough to write an essay. So if you want to use it more than that, you will have to pay.

Below is a chart of information we were able to find from Grubby's website. If it's stated by Grubby, we will say it's a claim.

Quick note about AutoTyper.

If you search for Grubby humanizer or AI Humanizer Grubby, they are all the same Grubby.ai product.

We could not find a Grubby Chrome extension when searching on the Chrome Web Store as of November 2026. So this review will be for the web app.

How We Scored Writing Quality on 3 Drafts

How do AI humanizers work? They will, most of the time, alter the words and flow of sentences (perplexity and burstiness), which can cause them to not be true to what you originally had. So here is our Grubby AI Humanizer review.

• Grubby mode: GPTZero, the default ("Optimized for GPTZero"), for all 3 drafts. Each run returned 2 drafts, and we scored Draft 1

• Drafts: 94, 88, and 92 words, generated by ChatGPT

• Plan: Grubby free plan. Phrasly Ultra on the Balanced setting, on a paid Unlimited account

• Test date: November 2026

Each output was scored on 4 things:

• Meaning kept: Does the rewrite say the same thing? (yes, partly, or no)

• Facts kept: Are numbers, names, and claims intact? (count of facts changed or dropped)

• Readability: Is it natural, with no tone drift or filler? (Flesch Reading Ease, calculated with textstat for both humanizers)

• Fixes needed: How many manual edits before the text is usable?

Any altered fact, meaning change, grammar mistake, or filler word is applied equally to all samples. This is our method for finding out if AI humanizers actually work. Which is why meaning preservation gets its own score.

These scores are for informational purposes.

Originality.ai sells a detector.

As you can see, it's easy to get a low score from an AI detector. But that doesn't mean your text still has the same meaning. We used Phrasly AI Humanizer (Ultra, Balanced Setting) to humanize these 3 samples.

You can see on the scorecard what kept the most meaning.

Sample 1: Academic Paragraph, Weak vs Strong Rewrite

Would you be fine handing this in as an essay you edited yourself? Grubby AI offers Academic (Turnitin), but as you can see from the results above, we were looking at how accurate and human it sounded, not Grubby AI Turnitin results.

Academic integrity depends on the writing being yours.

Can Grubby AI pass Turnitin? As shown by the results above, different AI detectors will give different results each time you run an essay. This was not our focus when writing this review.

Make sure to check with your school what their AI policy is before using any rewritten work.

Original (94 words, ChatGPT)

The Grubby Output

Here is what the Grubby AI Humanizer returned in GPTZero mode:

Grubby AI on the free plan in GPTZero mode, Sample 1 (academic). The counter shows 206 of 300 free words left after this 94-word run. The output is Draft 1 of 2.

• Citation: Kept in place, as "Walker (2017) highlights the impact that sleep can have".

• Hedged claims: "may suggest" became "could indicate," still hedged. But "often struggle" became "have also been shown". A stronger claim than the original makes.

• Technical terms: "memory consolidation" and "REM sleep" both kept.

• Generic essay tone: A clunky opener ("in various ways including") and "poor" twice in one sentence.

What We Had to Fix

• Meaning kept: "Sleep is crucial for memory consolidation throughout the day" moved consolidation to the daytime. Changed to "it lets the brain process and store what was learned during the day".

• Meaning kept: "have also been shown to have poor information processing" overstated the original. Restored "often struggle with recall".

• Readability: Rewrote the clunky opening list. Removed the repeated "poor" and hyphenated "sleep-deprived" (3 fixes).

Citations and hedges are where humanized academic text most often goes wrong.

The Stronger Rewrite

Grubby overperformed for us here. Citation was kept as well as the hedge and 2 of the technical terms. The student would have to correct one claim about consolidation and an over-stated claim.

Sample 2: Marketing Blog Paragraph, Weak vs Strong Rewrite

Marketing will be one of the first to see tone drift. So here is a test to see if Grubby maintains the brand voice. We used simple sentences second person. One product mention and one selling point.

We looked to see if it kept the brand voice. Did it add unneeded words? Would it have negatively affected the copy or SEO? By losing a keyword, adding more words to the sentence, or having a weaker lead in.

Original (88 words, ChatGPT)

The Grubby Output

Grubby's humanizer modes are named after detectors. Not writing styles. We kept GPTZero mode for a fair test. The Grubby AI Humanizer returned:

Sample 2 (marketing) in Grubby's GPTZero mode. PrepPal and the 3-hour benefit survive. The casual voice turns formal. 118 free words were left after this run.

• Word count: 88 → 84, so no padding.

• Voice shifts: "Meal planning need not be a time-consuming process" and "a list of items to purchase" turn a casual voice formal.

• Empty claims: None added. But "PrepPal allows you to plan and organize your food preparation" repeats the second sentence.

• Keyword and product name: PrepPal kept 3 times. "about 3 hours a week" kept as "approximately 3 hours a week".

What We Had to Fix

• Readability replaced the formal opener. And "a list of items to purchase" with plain wording (2 fixes).

• Readability removed the repeated "plan and organize" sentence. And changed "You will be saving approximately" to "It saves you about" (2 fixes).

• Readability added the missing comma before "which" (1 fix).

Padding and a lost keyword are SEO problems as well as style problems.

None of them touched a fact. All 5 were about voice and wording.

The Stronger Rewrite

Will AI humanizers work on clients’ copy? Kind of. Grubby left all the info from PrepPal in place. Including the 3 hours and everything. It just lost that informal feel. So we had to rewrite most of it.

Sample 3: Fact-Dense Report Paragraph, Weak vs Strong Rewrite

If one number is off, then the report is useless. So here is a sample of Grubby retaining facts. Since there are many facts, this is a good example of if a humanizer will keep the meaning of a text.

Original (92 words, ChatGPT)

The facts to track:

• Numbers: 18,400 tonnes, 214 collection points and 12%.

• Named entities: City of Leeds and Sarah Patel.

• Dates: 2024, compared with 2023.

• Causal claim: New kerbside bins led to the increase.

The Grubby Output

Here is the Grubby AI humanizer output. Checked fact by fact against the list above:

Sample 3 (report) in Grubby. The output grew from 92 to 104 words. Only 26 of the 300 free words were left after our 3 drafts.

• 18,400 tonnes: Kept, though "waste" became "recycling".

• 12% and 2023: Kept

• 214 collection points: Changed to "214 recycling collections," a different measure.

• City of Leeds, Sarah Patel and 2024: Kept.

• Causal claim: Same direction, but "was attributed to" became the ungrammatical "can be down to".

Grubby also added two filler sentences. Taking the paragraph from 92 to 104 words.

What We Had to Fix

• Facts kept: Restored "214 collection points" in place of "214 recycling collections".

• Meaning kept: Changed "18,400 tonnes of recycling" back to "waste" and "can be down to" to "was attributed to" (2 fixes).

• Readability: Cut the filler sentence, rewrote "helps the city in enhancing the waste system" and removed the repeated "have shown" (3 fixes).

There's only one error in facts, and something like that you would never know if you didn't have the original. So make sure to check your report after using any humanizer.

The Stronger Rewrite

Not without a fact check: Grubby kept 6 of the 7 facts. It turned 214 collection points into "214 recycling collections" and padded the paragraph with filler.

Fix-Count Scorecard for Grubby AI and Phrasly Ultra

Below is a table of all 3 runs from this Grubby AI humanizer review. Each one was graded using the same rubric used on each sample above.

Phrasly uses their Ultra tool. The 3 samples were run through ultra and graded with the same rubric by the same person.

Grubby had 3 rows completely. All were academic paragraphs: kept meaning and facts with less corrections (5 to 7). The marketing and report were tied in meaning and facts and had the same amount of corrections, at 16 to 16.

Phrasly Ultra had a higher readability score on all 3 of our drafts. It also required fewer corrections on our marketing and report draft.

When writing our academic paragraph, it had a high score, but it was very informal and used second person, which did not fit the task.

They both were able to keep all of the products and numbers/citations. The only difference was that Grubby had changed what 214 was for. And Phrasly had changed who the academic paragraph was about.

There were no false numbers from either. These are what Phrasly Ultra gave us.

Phrasly Ultra (Balanced) on Sample 1. Easier to read. But it dropped "memory consolidation", changed "university students" to "school" and switched to a casual tone (7 fixes).

Phrasly Ultra on Sample 2. PrepPal and "3 hours a week" were kept, with a sentence fragment, a capitalization slip, and an awkward question to fix (4 fixes).

Phrasly Ultra on Sample 3. Every number kept. The link between the new bins and the increase was weakened, and a speculative sentence was added (5 fixes).

Which kept your meaning more? We would say Grubby on these 3 drafts. Because of the academic paragraph. The other two were even. Below are detector scores just as a note. They do not play into our score for writing.

Is Grubby AI Free, and What Does It Cost?

There is a Grubby AI free version. Just not much. Grubby AI humanizer free offers 300 words a month, no credit card required. And you have to pay to use all of Grubby AI. It will be billed every 4 weeks or a year.

We tried Grubby AI humanizer for free. It gave us 300 words. As you can see, we only have 26 words left after 3 drafts.

Can Grubby AI humanizer be used for free? Yes, if your writing only requires 1 paragraph. Our 3 drafts totaled 274 words. How much is Grubby AI after that? Below are the Grubby AI pricing plans as of October 2026 from their pricing page.

That was all we needed for our testing. 274 out of the 300 words. If a student had a 1,500-word paper, they would need to use at least Essential. Which only allows you to paste 500 words at a time. You would have to paste the paper in 3 chunks. Pro allows you to paste 1,500 words.

Trustpilot had one user claim that Grubby charged them $19.88 without permission and did not give it back. So that's just one person. Grubby's refund policy and terms of service are covered in the next section.

All prices are up to date as of the time of writing. Check back on the pricing page for this tool to make sure the price is still accurate.

Turnitin Guarantee, Detector Scores and a Legit and Safety Check

Here is what other people have found and what Grubby has to say on the subject. This will not tell you how to not get caught.

What Detector Scores Can and Cannot Tell You

Originality.ai gave Grubby's work a 98% Likely AI score. On ZeroGPT, it got a 9.4% AI score, and the Writer AI detector said it was 100% human. The original scored 100% likely AI on Originality.ai. 100% on ZeroGPT and 85% human on Writer.

Originality.ai has their own detector they sell. Its conclusion names GPTZero even though it tested ZeroGPT.

So Grubby AI detector results depend on what detector you use, we guess. And GPTZero sells a detector.

Would you believe a humanizer if it told you your writing was 100% human? Probably not. Since its judging its own work, it's not really helping you out. AI detection scores differ by tool, and those scores change over time as they update their detectors.

This is why our scorecard measures writing quality instead.

What the Turnitin Guarantee and Terms Actually Say

Can Grubby AI give you a refund if your paper is detected? We would not expect that to happen. Turnitin’s guarantee page says, "If it doesn't pass, you don't pay".

However, in Grubby’s terms, under section 8.5, it states that "All purchases are non-refundable" except after a notified price increase.

The guarantee page also states there's a "99.8% Bypass Rate" for thousands of submissions to Academic mode. This claim by Grubby has no date, sample size, or stated method.

RewriteAI, which sells a humanizer of its own, reported the refund-policy page showed only the site's header and footer on October 3, 2026.

Section 6.2 of the terms also prohibits using the service to "engage in cheating or academic misconduct", which voids any student who depends on the guarantee. Also, detectors evolve, so no warranty is forever.

Is Grubby AI Legit and Safe? A Quick Checklist

Is Grubby AI legit? It is a real paid product. But check these points before you pay:

• Trustpilot reviews: 3.0 out of 5 from 55 reviews on Trustpilot in November 2026. Praise for price and complaints about billing and output.

• User complaints: Reviewers describe "totally unstable output" that "changes the topic completely" (February 2026). Refund requests met with "all sales are final" (December 2025).

• Billing: The unrefunded $19.88 charge reported in March 2026, covered in the pricing section.

• Privacy: None of the reviews we read quote Grubby's privacy policy on stored text. Read it yourself before pasting anything confidential.

• AutoTyper access: It uses your Google account. According to RewriteAI, Grubby stores Google authorization tokens during a session for up to 7 days. You can revoke its access through your Google account settings when you're done with it.

• Academic integrity: Using a humanizer to submit work that is not your own can breach school policy, whatever a detector says.

Grubby claims over 1.6 million students have utilized its humanizer and around 14,000 students utilize it weekly. These statistics are self-reported by Grubby, not from a third party.

Compare Grubby AI Alternatives Before You Pay

They have different purposes, so the best Grubby AI Humanizer alternative depends on if you want paraphrasing, grammar assistance, or a rewrite that preserves meaning and facts.

• Undetectable AI: Suits writers who want a humanizer and detector in one place. Its pitch is about detector scores rather than meaning.

• QuillBot: Suits students already using its paraphraser. Paraphrasing can blur technical terms.

  See this QuillBot AI Humanizer review.

• Grammarly: Suits writers who want grammar help next to rewriting. Inside Grammarly's own editor.

  See Grammarly AI Humanizer tested on 3 drafts.

• WriteHuman: Suits users who want a dedicated humanizer with a small free allowance. It reportedly runs HumanizerBench. A benchmark that also ranks its own tool.

• StealthWriter: Suits users focused on detector scores. Like Grubby, it says little about meaning or fact retention.

On Grubby AI vs Undetectable AI, neither publishes meaning or fact-retention data. Test both on your own draft. Searches like "Undetectable AI Humanizer Grubby AI" usually come from the same question: which one keeps the writing right?

Improve Your Own Draft with Phrasly AI Humanizer Ultra

Grubby preserved meaning better here, although just a bit better. On our scorecard, Grubby won meaning, facts, and fixes on Sample 1, and Ultra won readability on all 3 drafts as well as fixes on Samples 2 and 3.

Phrasly AI Humanizer Ultra is included with Phrasly's paid Unlimited plan starting at $10.99/month billed annually.

Prices listed are accurate at the time of article publication and may change over time. Please check the individual tools pricing page for current price before purchasing.

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