Undetectable AI vs QuillBot vs Grammarly AI Humanizer

Undetectable AI on the headline, with a condition: the $5.00 is a yearly toggle and the charge is $60.00 up front; the monthly toggle is $9.99, both read 9 November 2026. QuillBot Premium is $8.33 a month billed annually with a $5.00 promotional rate shown on the day of reading, and Grammarly Pro is $12 with no billing period on the card, both read 9 November 2026. What each price buys differs more than the prices do. Undetectable AI's $60.00 buys a humanizer and 10,000 words a month. QuillBot's $99.96 buys the paraphraser, grammar checker, a plagiarism checker with a 25,000-word-a-month allowance, an AI detector, a 6,000-word summarizer and the humanizer with Advanced mode. Grammarly's Pro buys the grammar product with the Humanizer agent, Grammarly's own AI detector, citation tools and an authorship record, all read 9 November 2026.

All read 9 November 2026. A reader who wants only a humanizer pays least at Undetectable AI and pays for nine other tools at QuillBot; a reader who already pays for either suite gets the humanizer for no extra money. Price is reported on this site and never scored.

The two that renew. QuillBot's Basic mode accepts 125 words per input with no stated end, read 9 November 2026; Grammarly's free account renews 100 AI prompts a month and the free tool on its product page runs with no account, read 9 November 2026. Undetectable AI's 250 words is one long paragraph and then the paywall, checked 8 November 2026. The protocol's inputs run 350 to 500 words, so none of the three free tiers takes a protocol input whole: Undetectable AI's trial is 100 words short, QuillBot's input is split into three or four pieces, and Grammarly's row depends on a cap the vendor does not print.

All read on the dates above. The free tier that takes a full essay whole belongs to none of these three; Clever AI Humanizer accepts 3,000 words per request with no sign-up, checked 8 November 2026, and leads the free-tier table on the site's free ranking.

Three stances. Undetectable AI's name is its claim, and its pricing page publishes no accuracy figure this site could quote with a source, read 9 November 2026. QuillBot's humanizer page describes a rewrite that reads as natural writing and makes no detector statement in the page read, 9 November 2026. Grammarly's product page states that the tool is not intended to get past AI detectors, works on clarity and coherence instead, and asks users to acknowledge AI assistance in academic or professional work, read 9 November 2026; among the twelve tools in the ranking, Grammarly is the one vendor that declines the detector claim.

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). All three tools are paraphrasers, so readings may move under any of them, whether or not the vendor aims at them, and a reading is true for its date.

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 against its input and five named detectors read on the run date. Undetectable AI, which names no modes, has one row; QuillBot has Basic and Advanced; Grammarly has the default voice only, since a custom voice is not a documented strongest mode. No detector score should be the only evidence in a misconduct case.