The signs of AI writing, measured
August 9, 2026 · View on GitHub
The eight structural patterns below are what actually move an AI detector, ranked by how hard they hit. Missing contractions are the single strongest signal: "The software has been significantly improved" scores 92.6% AI, while "software's got a lot better" — the same fact, contracted — scores 0.03%. Formal verbs are next: "provides excellent stability" scores 99.6%, "doesn't flex" scores 0.01%. Every number here comes from a paired test, the same information written twice.
The finding underneath all of it: detectors have learned what clean, balanced, professional prose looks like, because that's what AI writes. Formality is the tell, not vocabulary. There's no word list to avoid.
Tested: 70+ paired sentence variations, February 2026
Model: desklib/ai-text-detector-v1.01 (DeBERTa-v3-large, 304M parameters, RAID benchmark #1)
Previous model: dejanseo/ai-cop (DeBERTa-v3-small fine-tune) — replaced 2026-02-16
Tool: ai-detect (see the README) — run any of these yourself
How the tests were run
Each test was a paired comparison: a formal, AI-style sentence against a conversational rewrite carrying the same information. Pairing matters — it isolates structure from subject, so the gap can only come from how the sentence is built. Score one sentence on its own and you learn very little; write the same fact two ways and you can see what the model's reacting to.
The eight patterns
1. Contractions Are the #1 Signal
| Without contraction | AI prob | With contraction | AI prob |
|---|---|---|---|
| "The software has been significantly improved" | 92.6% | "Software's got a lot better" | 0.03% |
| "Fanatec is not the cheapest option available" | 53.4% | "Fanatec aren't cheap" | 0.05% |
| "They have partnered with several leading brands" | 98.8% | "They've partnered with Porsche, BMW, Bentley" | 0.01% |
2. "Provides/Offers/Delivers" Are Detector Magnets
| With formal verb | AI prob | With colloquial verb | AI prob |
|---|---|---|---|
| "provides excellent stability" | 99.6% | "doesn't flex" | 0.01% |
| "offers comprehensive software support" | 99.9% | "app's actually pretty good now" | 0.01% |
| "delivers impressive performance" | 92.5% | "genuinely impressive for what you're paying" | 17.0% |
| "encompasses multiple price points" | 99.5% | "ranges from basic stuff to high-end" | 0.02% |
3. "For [group] who [condition]" Is a Strong AI Signal
| AI frame | AI prob | Human frame | AI prob |
|---|---|---|---|
| "For PC-only buyers who don't need console support, Moza offer..." | 99.1% | "If you don't care about PlayStation, Moza will save you money" | 0.8% |
| Same, subject-first variant | 86.8% | "No PlayStation? Moza are cheaper" | 1.2% |
4. Formal Transitions Are Instant Flags
| With transition | AI prob | Without | AI prob |
|---|---|---|---|
| "Additionally, the QR2 provides..." | 99.6% | "The QR2 doesn't flex and..." | 0.01% |
| "Furthermore, Fanatec offers..." | 99.9% | "The Fanatec app replaced FanaLab and..." | 0.01% |
| "In conclusion, Fanatec remains..." | 99.9% | "Look, Fanatec make good kit" | 0.05% |
| "It's important to note that..." | 99.8% | "Prices vary by region, obviously" | 0.12% |
| "This represents a significant upgrade" | 99.8% | "Massive upgrade over the old version" | 0.8% |
5. Specific Names Beat Vague Abstractions
"several leading automotive brands" → 98.8% AI "Porsche, BMW, Bentley and the WRC" → 0.01% AI
6. Trailing Opinions Lower AI Probability
Removing a trailing personal clause ("and I haven't seen much disagreement on that") INCREASED AI probability from 1.6% to 18.6%.
7. Patterns That Always Pass as Human
- Typos: 0.0% AI
- Colloquial idioms ("how far down the rabbit hole"): 0.25% AI
- "I reckon" + trailing "honestly": 0.3% AI
- Fragment questions ("No PlayStation?"): 2.9% AI
- Short blunt statements ("Fanatec aren't cheap"): 0.05% AI
- Dash-interrupted sentences with opinion: 0.01-0.03% AI
- Possessive contractions ("Software's got"): 0.03% AI
8. The Word "Noticeably" Is Flaggy
"The consensus has shifted noticeably" triggers AI regardless of framing (78-82% AI). "The mood has definitely changed" passes (5.4% AI).
The rule underneath all eight
Simplify, don't engineer. Every formal construction has a casual equivalent that reads as human. The detector has learned what clean, balanced, professional prose looks like — and that's what AI writes. Write like you're explaining something to a mate, not writing a press release.
What this is not
It isn't a guide to beating a detector. The patterns run one way: formal phrasing reads as machine-written because machines are trained on formal phrasing, so fixing a flagged sentence and fixing a badly written one are the same edit. Contract the verbs, name the actual brands, put the opinion back in.
It also isn't a verdict engine. A confident writer who contracts their verbs sails through, and a careful human writing a spec sheet will flag. Across a batch of forty articles the signal is real; on any one sentence it is a prompt to look closer, not a finding.
Checking your own text
pip install .
ai-detect --file draft.md
Every sentence is scored, and every flagged one comes back with the pattern that triggered it and a plain rewrite. The full tool, the model choices and the privacy position are in the README.