# AI content detectors and humanizers compared: Originality.ai vs GPTZero vs Undetectable AI vs QuillBot

By Seventh Feed Editorial, who works on Seventh Feed.

Data as of 2026-11-11.

Editorial teams use AI detectors to audit freelance submissions, while writers use paraphrasers and humanizers to remove repetitive machine phrasing. We tested Originality.ai, GPTZero, Undetectable AI, and QuillBot across three samples: an unedited LLM draft, a heavily edited technical guide, and a human-written essay from 2019.

Originality.ai ($14.95/mo) is the strictest classifier for content agencies and includes plagiarism and fact-checking in the same scan. GPTZero ($14.99/mo, with a 10,000-word free tier) gives the clearest sentence-level breakdown and lowest false positives on technical docs. Undetectable AI and QuillBot focus on rewriting stiff sentences.


## Tools

- Originality.ai (originality.ai): paid, from $14.95/mo (or $30 pay-as-you-go), 3.4M visits/month
- GPTZero (gptzero.me): freemium, from $14.99/mo, 17.5M visits/month
- Undetectable AI (undetectable.ai): freemium, from $14.99/mo, 2.6M visits/month, llms.txt
- QuillBot (quillbot.com): freemium, from $8.33/mo, 62M visits/month

Page: https://seventhfeed.com/compare/ai-content-detectors-and-humanizers