aifingerprint 1.0.1

Detect AI writing patterns — scores text 0-100 for AI fingerprints

aifingerprint

Scores text 0–100 for AI writing fingerprints. Catches the stuff LLMs can't help doing — flat rhythm, hedge words, compression patterns, that weird punctuation sameness. No API keys, no model downloads, just stdlib Python.

Installation

pip install .
# or for development:
pip install -e .

Usage

# Analyze a file
aifingerprint input.txt

# Read from clipboard
aifingerprint --clipboard

# Read from stdin
echo "text to analyze" | aifingerprint

# Generate a markdown report
aifingerprint input.txt --report
aifingerprint input.txt --report output.md

Score interpretation

Score	Label	Meaning
0–20	CLEAN	Looks human
21–40	MILD	A few AI-ish traits, probably human
41–60	NOTICEABLE	Smells like AI
61–80	OBVIOUS	Yeah, that's AI
81–100	BLATANT	Copy-pasted straight from ChatGPT

What it checks

Ten weighted checks, each scoring 0.0–1.0:

Check	Weight	What it measures
Compression	20%	LZMA similarity to a known AI corpus
Sentence rhythm	15%	Coefficient of variation in sentence lengths
Tone	15%	Hedging, enthusiasm, formality, word length
Punctuation	12%	Shannon entropy of punctuation distribution
Connectives	10%	Density of discourse markers (however, moreover...)
Burstiness	8%	Whether content words cluster or distribute evenly
Vocabulary	8%	Known AI-favored words (delve, leverage, utilize...)
Structure	7%	Paragraph uniformity, parallelism, five-paragraph essay
Phrases	5%	Cliches, hedges, openers, closers
Formatting	0%	Em dashes, bold bullets, header density (disabled)

HTML reports

Generate a markdown report, then convert to styled HTML:

aifingerprint input.txt --report
python -m aifingerprint.html report.md

How it compares

We tested against the RoBERTa OpenAI detector (openai-community/roberta-base-openai-detector via HuggingFace Transformers) — the only other pip-installable thing that runs offline on prose. 27 samples, 8 AI-generated, 19 human-written:

	aifingerprint	RoBERTa
AI samples (avg)	58%	97%
Human samples (avg)	18%	97%
Separation	40pp gap	~0 — labels everything as AI

RoBERTa was trained on GPT-2 output back in 2019. It thinks Paul Graham, Reddit posts, and Seth Godin are all 100% AI. Basically useless on anything written after 2022. aifingerprint uses heuristics instead of a model, so it doesn't go stale when the next GPT drops.

Other packages in this space:

Package	Why it doesn't work
gptzero	API wrapper — requires paid GPTZero API key
openai-detector	Thin wrapper around the same broken RoBERTa model
sloppylint	Detects AI patterns in code, not prose
finbert-ai-detector	Fine-tuned for financial documents only
ai-slop-detector	Browser-based, requires Gemma 270M model download
textstat	Readability metrics (Flesch, SMOG, etc.) — doesn't attempt detection

No dependencies

Runs on Python 3.10+ using only the standard library.