I got mass-flagged by GPTZero for my own writing. So I built an open-source alternative in pure Python.

#showdev #ai #opensource #python

Every AI text detector is either paid or closed-source.

GPTZero charges $15/month. Originality.ai charges per scan. Turnitin locks you into institutional contracts. And all of them are black boxes — when they flag your text as AI-generated, you have no idea why.

I got tired of this. Especially after GPTZero flagged my own human-written paragraphs as "98% AI."

So I built lmscan.

What it does

pip install lmscan
lmscan "paste any text here"
→ 82% AI probability, likely GPT-4

It analyzes 12 statistical features — burstiness, entropy, Zipf deviation, vocabulary richness, slop-word density — and fingerprints 9 LLM families.

No neural network. No API key. No internet. Runs in <50ms.

The detection approach

AI text is unnaturally smooth. Humans write in bursts — short punchy sentences followed by long rambling ones. LLMs produce eerily consistent sentence lengths.

LLMs also have vocabulary tells:

GPT-4 loves "delve" and "tapestry"
Claude says "I think it's worth noting"
Llama overuses "comprehensive" and "crucial"

lmscan scores text against each family's marker set to fingerprint the source.

Python API

from lmscan import scan
result = scan("your text")
print(f"{result.ai_probability:.0%} AI, likely {result.fingerprint.model}")

Features

12 statistical features (burstiness, entropy, Zipf deviation, hapax legomena, vocabulary richness, slop-word density, and more)
9 LLM fingerprints (GPT-4, Claude, Gemini, Llama, Mistral, Qwen, DeepSeek, Cohere, Phi)
Multilingual support (English, French, Spanish, German, Portuguese + CJK auto-detection)
Batch directory scanning with --dir
Mixed-content paragraph analysis with --mixed
HTML reports with --format html
Streamlit web UI with pip install lmscan[web]
Pre-commit hook integration
Calibration API for tuning thresholds on your own data