Undetectable AI vs Grubby AI

Undetectable AI for a single long essay, because it states no request cap; for a month of short pieces the two entry plans hold the same 10,000 words. Undetectable AI's entry plan is 10,000 words a month with no per-request cap, read 9 November 2026, so a 1,500-word essay goes through whole and six of them fill the month with 1,000 words left. Grubby's Essential plan is also 10,000 words a month, capped at 500 words an input, read 9 November 2026, so the same essay is three inputs, rewritten without sight of each other, and the month holds the same six essays in eighteen pieces.

Both read 9 November 2026. The pattern that favours Grubby is a writer who wants three named modes and a free allowance that renews, and will pay $119.88 a year for Pro to get them with a 1,500-word cap. The pattern that favours Undetectable AI is anyone whose pieces run past 500 words and who wants the lower price on either billing term. Price is reported on this site and never scored.

Grubby's, on recurrence; neither is enough to judge a tool. Grubby gives 300 free words a month to every new user, read 9 November 2026, and the allowance renews. Undetectable AI gives 250 words in total, checked on 8 November 2026, and the trial does not renew. Over three months that is 900 free words against 250, and either figure is one long paragraph at a time.

What the free words show also differs. Grubby's free tier does not state which mode it runs or its input cap, read 9 November 2026, so a free user cannot tell whether the paid Simple mode reads the same. Undetectable AI names no modes on any plan, so its 250 trial words are the same service as the paid plan, only shorter.

Both read 9 November 2026 except the Undetectable AI trial size, checked on 8 November 2026.

The two vendors sell the same promise in different registers. Undetectable AI's name is its claim, and its pricing page publishes no accuracy figure that this site could quote with a source, read 9 November 2026. Grubby's pricing page leads with a money-back guarantee tied to Turnitin's AI detector, states that Grubby is the only humanizer to offer one, and repeats on every plan tile a claim of a 100 percent human score and of clearing all detectors including GPTZero, with no input set, detector version or date, read 9 November 2026. A refund is a commercial term, not a measurement, and this site scores neither.

Turnitin's own page is the relevant counterweight. Turnitin states that its AI writing checker helps identify when AI bypassers, which it also calls humanizers, may have been used in a submission, alongside AI-paraphrased text (Turnitin, AI writing detection page, read 9 November 2026). Turnitin's detector is not available to the public, so this site relies on Turnitin's published statements and peer-reviewed studies, and no page here states a Turnitin pass or fail for any tool.

Weber-Wulff and colleagues tested 14 AI text detectors and found every one below 80 percent accuracy, with accuracy falling further on paraphrased and machine-translated text (Weber-Wulff et al. 2023, International Journal for Educational Integrity, read 9 November 2026). Paraphrasing moves detector readings; what the study does not measure is whether the rewrite kept the writer's claims. The published method weights meaning kept at 35 points of 100, errors added at 20, detector pass rate at 30 and limits and access at 15, with two editors rating every output blind. When a run is published, this page gains those fields for both tools; a run will show Grubby on Simple and on Enhanced and Undetectable AI on whatever its interface shows. No detector score should be the only evidence in a misconduct case.