HumanProse vs QuillBot vs Undetectable AI — Real Scores Compared
We tested them all. Here's what actually happened.
Every AI humanizer claims to produce "undetectable" text. We wanted to see who delivers and who doesn't. So we took a 500-word ChatGPT essay, ran it through three tools — HumanProse, QuillBot, and Undetectable AI — and tested every output against six popular detectors.
No cherry-picking. No "best case" samples. One input, three tools, six detectors.
The test setup
Input text: 500-word ChatGPT-4 essay on renewable energy policy. Raw AI score: 94% on our internal scorer, 100% on GPTZero. Tools tested:- HumanProse (Starter plan, $9.99/mo)
- QuillBot (Premium, $9.95/mo)
- Undetectable AI (monthly plan, $9.99/mo)
The results
Heuristic detectors (ZeroGPT, Sapling, internal)
This is where the tools actually work — and where meaningful differences show up.
| Tool | ZeroGPT | Sapling | Internal Score |
|------|---------|---------|----------------|
| Raw ChatGPT | 88% AI | 99% Fake | 94% AI |
| HumanProse | 17.5% AI | 0.5% Fake | 12% AI |
| QuillBot | 43% AI | 34% Fake | 38% AI |
| Undetectable AI | 22% AI | 8% Fake | 19% AI |
HumanProse and Undetectable AI both pass heuristic detectors consistently. QuillBot struggles — it's a paraphraser, not a humanizer, and the distinction matters.
Neural detectors (GPTZero, Copyleaks, Originality.ai)
Here's where the honest truth comes in. None of the tools beat neural classifiers.
| Tool | GPTZero | Copyleaks | Originality.ai |
|------|---------|-----------|----------------|
| Raw ChatGPT | 100% AI | 100% AI | 100% AI |
| HumanProse | 100% AI | 100% AI | 100% AI |
| QuillBot | 100% AI | 100% AI | 100% AI |
| Undetectable AI | 100% AI | 100% AI | 100% AI |
Every tool scored 100% AI on all three neural detectors. Despite what their marketing says.
Why QuillBot falls short
QuillBot is a solid paraphrasing tool. But paraphrasing and humanization are different things. QuillBot swaps synonyms and restructures sentences. It doesn't address the statistical signals detectors actually measure — sentence length variance, vocabulary diversity, transition patterns, paragraph uniformity.
The result? Detectors still see the same patterns under different words.
Why Undetectable AI's claims don't hold up
Undetectable AI's landing page says it beats GPTZero, Originality.ai, and Copyleaks. In our testing, it scored 100% AI on all three. To be fair, it does well on heuristic detectors — ZeroGPT and Sapling results were solid. But the headline claims are misleading.
Where HumanProse fits
We'll be direct about this: HumanProse doesn't beat neural detectors either. No tool on the market reliably does. What we do is reduce AI scores significantly on heuristic-based detectors (ZeroGPT, Sapling, and similar tools) through multi-pass rewriting that targets specific statistical signals.
We're transparent about this because we'd rather you know what you're paying for.
The price comparison
| Tool | Price | Word limit | What you get |
|------|-------|------------|--------------|
| HumanProse Starter | $9.99/mo | 30,000 words | Multi-pass humanization, free detection |
| QuillBot Premium | $9.95/mo | Unlimited paraphrasing | Synonym-level rewriting only |
| Undetectable AI | $9.99/mo | 10,000 words | Humanization with inflated marketing claims |
At the same price, HumanProse gives you 3x the word limit of Undetectable AI and actually addresses detection signals (unlike QuillBot). Plus free AI detection scoring for unlimited texts — no subscription needed.
Bottom line
If you need to pass heuristic detectors like ZeroGPT and Sapling, HumanProse and Undetectable AI both work. HumanProse gives you more words for the money and doesn't lie about beating GPTZero.
If you need to pass GPTZero or Originality.ai, no tool currently does this reliably. Anyone claiming otherwise isn't being honest with you.
We'd rather be the tool you trust than the one that overpromises and underdelivers.
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