Undetectable AI vs. Decopy AI: Will They Detect AI Writing?

AI writing detectors have gotten smarter — but so have AI writers. What used to be an easy game of “spot the bot” has turned into an elaborate chase where detectors try to flag AI content that’s now eerily close to human writing.

So today, we’re testing two tools that claim to be able to tell the difference: Undetectable AI’s Detector and Decopy AI’s Detector. Both promise high accuracy rates and enterprise-grade reliability. But like most tools in this space, what’s promised and what’s actually delivered don’t always line up.

This isn’t just about numbers — it’s about consistency, readability, and how each detector handles the gray areas. Let’s find out.

What is Undetectable AI

By now, Undetectable AI has become a major name in the AI writing space. What started as an AI humanizer quickly evolved into a complete writing ecosystem — with tools for rewriting, detecting, summarizing, and even generating resumes and essays that sound undeniably human.

Its AI Detector works as part of that larger suite, designed to catch AI-written text across essays, blog posts, academic papers, and business content. The promise? A strong accuracy in identifying content from large language models.

And because it’s part of a broader ecosystem, it integrates naturally with the humanizer — letting you detect, rewrite, and verify your content all in one place.

What Is Decopy AI?

Decopy AI is a platform for writers. It was designed primarily as a free content authenticity checker for students, researchers, SEO managers, and professionals who need to ensure their work is genuinely human-written.

One thing Decopy does particularly well is its multi-functionality. Alongside detection, it offers an AI Humanizer, Summarizer, and even a Grammar Fixer — but these tools feel a bit more scattered compared to Undetectable AI’s cohesive workflow. Still, if you just need a quick detection scan, Decopy AI’s minimalist interface and direct results are easy to use.

Undetectable AI vs. Decopy AI: Detecting AI Writing

Test #1

The AI-Generated Essay:

Undetectable AI: Correctly identified writing as machine-generated.
Correctness: 99%

Decopy AI: Correctly identified writing as machine-generated.
Correctness: 91%

Test #2

The AI-Generated Essay:

Undetectable AI: Correctly identified writing as machine-generated.
Correctness: 93%

Decopy AI: Correctly identified writing as machine-generated.
Correctness: 82%

Test #3

The AI-Generated Essay:

Undetectable AI: Correctly identified writing as machine-generated.
Correctness: 99%

Decopy AI: Correctly identified writing as machine-generated.
Correctness: 66%

Test #4

The AI-Generated Essay:

Undetectable AI: Correctly identified writing as machine-generated.
Correctness: 99%

Decopy AI: Correctly identified writing as machine-generated.
Correctness: 60%

Test #5

The AI-Generated Essay:

Undetectable AI: Correctly identified writing as machine-generated.
Correctness: 99%

Decopy AI: Correctly identified writing as machine-generated.
Correctness: 91%

Test #6

The AI-Generated Essay:

Undetectable AI: Correctly identified writing as machine-generated.
Correctness: 99%

Decopy AI: Correctly identified writing as machine-generated.
Correctness: 94%

Test #7

The AI-Generated Essay:

Undetectable AI: Correctly identified writing as machine-generated.
Correctness: 99%

Decopy AI: Correctly identified writing as machine-generated.
Correctness: 80%

Average Score

What Now?

After testing both tools side by side, the results speak for themselves.

Undetectable AI’s Detector came in with an impressive 98.14% correctness, catching every AI-written piece with near-perfect precision. It didn’t just identify the obvious stuff — it picked up subtle traces in hybrid and humanized text, the kind that usually flies under the radar. 

Decopy AI, meanwhile, performed decently at 80.57% correctness — a respectable score, but it struggled in that gray middle area. It could catch pure AI text just fine, but when sentences became more naturally structured or slightly humanized, the accuracy dipped.

The difference comes down to depth. Undetectable AI doesn’t just look for patterns — it reads the rhythm, flow, and subtle imperfections that make writing human. And that’s why its results feel more balanced and believable.

If you just need a quick yes-or-no answer, Decopy AI works. But if you’re serious about catching AI content accurately and responsibly — especially in a world where humanized AI text is everywhere — Undetectable AI is the clear winner.