AI writing detection is getting messier by the month. Tools keep coming out with bold claims — “99% accuracy!” “Zero false positives!” “Best for schools!” — and yet, when you actually test them, half of them crumble the moment you feed them a paragraph written by anything newer than GPT-3.
Two tools that have been gaining attention lately are Undetectable AI and Pangram Labs’ AI Detector, which positions itself as more of a tech-forward academic tool. Both promise accurate AI detection, both say they work across different models, and both claim strong reliability. But in practice, claims mean nothing unless you actually test them side-by-side.
That’s what this comparison is for. We’re going to break down how each tool works, what they claim to do, and what their general strengths and weaknesses are — and then I’ll leave an empty section for my own accuracy tests.
What in Undetectable AI?
This AI Detector is part of the Undetectable AI ecosystem, which includes its famous AI humanizer, human-sounding rewrite tools, its resume builder, and a handful of quality-of-life writing tools.
But the AI Detector is one of their newer additions — and it’s built to handle the modern landscape of AI writing. That means:
- It checks text using multiple internal detection models
- It accounts for modern LLM styles
- It analyzes sentence rhythm, semantic patterns, predictability, and statistical irregularities
- It returns a clean, simple score instead of a confusing chart of “burstiness” and “perplexity”
One thing Undetectable AI does really well is avoiding the old-school detector problem of false positives from ESL writers. The tool tends to be conservative with flagging text, which is a good thing. I’d rather have a detector that doesn’t panic at the sight of a short sentence.
What is Pangram Labs?
Pangram Labs takes the more “academic integrity” approach — meaning the detection is built around formal writing, structured arguments, and long-form content. Their detector emphasizes:
- Identifying AI-generated sequences
- Sentence-level probability analysis
- Pattern recognition for over-polished, over-structured writing
- A scoring system meant for essays, reports, and academic writing environments
To be clear, Pangram Labs is not bad, it’s just different. It’s just built with a different philosophy in mind. Rather than avoiding false positives, it tries to cast a wider net.
Oh, and one other thing: unlike Undetectable AI, Pangram is not free. You get four free AI checks, but that’s it. No AI likelihood scores either, at least in the free version. So if you need something that’s more bang-for-your-buck, then go for Undetectable AI instead.
Testing Undetectable AI’s Detector vs. Pangram Labs
Test #1
AI-generated Text:
Undetectable AI: Correctly identified text as AI-generated.
Pangram Labs: Correctly identified text as AI-generated.
Test #2
AI-generated Text:
Undetectable AI: Correctly identified text as AI-generated.
Pangram Labs: Correctly identified text as AI-generated.
Test #3
AI-generated Text:
Undetectable AI: Correctly identified text as AI-generated.
Pangram Labs: Correctly identified text as AI-generated.
Test #4
AI-generated Text:
Undetectable AI: Correctly identified text as AI-generated.
Pangram Labs: Correctly identified text as AI-generated.
Test #5
AI-generated Text:
Undetectable AI: Correctly identified text as AI-generated.
Pangram Labs: Correctly identified text as AI-generated.
Test #6
AI-generated Text:
Undetectable AI: Correctly identified text as AI-generated.
Pangram Labs: Correctly identified text as AI-generated.
Average Score
The Bottom Line
After running them through my tests, both Undetectable AI and Pangram Labs’ AI Detector hit 100% accuracy — which is honestly impressive for both. You don’t see that very often, especially with the newer wave of AI models that tend to slip past older detectors.
But here’s where the difference actually shows up:
One is free, the other isn’t. So, in short:
Both are accurate. Both are reliable.
But Undetectable AI’s Detector gives you that same performance without the price tag.
