QuillBot vs GPTZero: Rewrite the Text or Check Its Origin

The short answer: if your job is checking where freelance or agency drafts came from, GPTZero is the specialist: free for 10,000 words a month, then Premium at $23.99 a month on monthly billing, or $12.99 a month billed annually, for 300,000 words (GPTZero pricing, checked on 26 October 2026). If your job is reworking copy, QuillBot is the rewriting tool, and its own AI Detector is free for all users (QuillBot detector article). Neither vendor presents a detection score as proof, and neither should you.

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This pair gets searched together for an uncomfortable reason: one tool rewrites text, the other tries to tell whether a machine wrote it. Everything below comes from what the two vendors publish about their own products. This page makes no accuracy claim of its own.

Before you run a single scan:

1. Size the word count. For example, a team that receives twelve 1,500-word drafts a month checks 12 x 1,500 = 18,000 words, more than GPTZero's free 10,000 and far inside Premium's 300,000 (GPTZero pricing).
2. Start from the process you already have. Ask writers for version history or drafts as a standard part of delivery. GPTZero itself recommends asking for artefacts of the writing process, such as Google Docs edit history, after a positive detection (GPTZero FAQ).
3. Decide what a flag triggers. Write down, before the first scan, that a flag opens a conversation with the writer and nothing else. Then count how many flags turn out to matter after that conversation.

In each vendor's own words

From QuillBot's articles on its detector's price, paraphrased text being flagged, human text being flagged and its API, and GPTZero's FAQ and pricing page, read on 26 October 2026.

Where the two sets of claims meet

Each vendor sells one side of the question

QuillBot's Paraphraser rewrites in modes from Fluency to Creative, and one Premium mode, Humanizer, is described as making text less robotic and as especially helpful for AI-generated drafts (modes). QuillBot's Humanizer article adds that it does not try to trick AI detectors or promise undetectability (Humanizer article). GPTZero, for its part, lists paraphraser and AI bypasser detection in the plan comparison for Premium and Professional (pricing).

What GPTZero says about its own limits

GPTZero's FAQ is specific. Accuracy rises with the amount of text, so a whole document is judged more reliably than a paragraph, and a paragraph more reliably than a sentence. Most of its training data is English prose written by adults. Its classifier is not trained to identify AI text that was heavily modified after generation, and it can flag machine-generated or highly procedural text, so it should be used on descriptive passages (GPTZero FAQ). Its how-it-works page says it prioritises keeping false positives low, because a student wrongly flagged costs more than an AI text missed (how it works).

What QuillBot says about detection

QuillBot says detectors sometimes produce false positives and that, while it aims for high accuracy, no tool is perfect (human text flagged). Read together, the two vendors agree on one thing: a score starts a question. It does not end one.

Prices, checked on 26 October 2026

GPTZero, in USD from its pricing page, checked on 26 October 2026, by the volume you check:

The plan comparison allows batch uploads of 50 files on Premium and 250 on Professional, and a Professional team plan bills per seat, from 2 seats, card only. QuillBot's AI Detector costs nothing; its Premium plan, which carries the extra Paraphraser modes and uploads of up to 20 files at once to the detector, is priced by region and shown at checkout (pricing article, file uploads).

GPTZero's API as a triage flag, not a judge

GPTZero's API returns a document_classification of HUMAN_ONLY, MIXED or AI_ONLY, a probability for each class, and the sentences it believes were AI-written; GPTZero says it does not store documents sent to the API (GPTZero FAQ). An agent or a small script can call it on every draft that lands in the content folder and post the result in the editor's channel.

The human step is the whole point. A MIXED or AI_ONLY result goes to the editor, who reads the highlighted sentences, asks the writer for drafts or version history, and decides. Nothing is rejected automatically, and nothing is said to the writer before the editor has looked. That follows GPTZero's own guidance that its sentence highlights should not be used alone to conclude that a document contains AI.

What it costs to start: nothing

Both detectors have a free door: QuillBot's is free outright, GPTZero's covers 10,000 words a month (QuillBot detector, GPTZero pricing). Before either, ask writers how they work and agree in the brief what AI help is acceptable. That conversation settles more than any score.

Look at what the two price lists sell, side by side: QuillBot charges for Humanizer as a Premium mode, and GPTZero charges for paraphraser and bypasser detection on its paid plans. A team that sits between them can pay both vendors for opposite halves of the same question, which an editor's read and a writer's version history answer for free.

Which one, for which job

• Choose QuillBot if your job is rewriting and tightening copy you or your team wrote, with a free detector to hand.
• Choose GPTZero if your job is checking drafts at volume, with documented limits, batch uploads and an API, as one input to an editor's judgement.

GPTZero is now owned by Superhuman, the company behind Grammarly (Superhuman announcement); it is still sold on its own site. Related entries: QuillBot, Grammarly and Superhuman. How to use QuillBot covers the rewriting side.

FAQ

Is GPTZero part of Grammarly now?

Part of the same company. Superhuman, which owns Grammarly, announced on 30 September 2026 that GPTZero is now part of Superhuman and that its detection suite will come to Superhuman Go (Superhuman announcement).

Will QuillBot output pass an AI detector?

QuillBot does not claim it will. It says the Paraphraser is not designed to avoid detection and that paraphrased or even human-written text can be flagged (QuillBot article).

Does GPTZero work in languages other than English?

GPTZero says its model supports English, Spanish, French, German and other languages, and that most of its training data is English prose; Premium lists multilingual detection (GPTZero FAQ, pricing).