You're reading an article, an email, or a student essay, and a quiet thought surfaces: did a person actually write this, or did a machine? Something about it feels a little too smooth, too even, too free of the small imperfections that usually mark human writing. You're not imagining it. AI-generated text has patterns — and once you know them, you start seeing them everywhere.
This guide walks through the real signs that text was written by AI, why they appear, and — just as importantly — why none of them is proof on its own. Spotting AI writing is about probability, not certainty.
Why AI Writing Has a "Tell"
Large language models generate text by predicting the most likely next word, over and over. That process produces writing that is fluent, grammatical, and remarkably consistent — but also, often, a little characterless. Human writing is shaped by mood, habit, and the odd tangent. Machine writing tends toward the statistical middle: safe, balanced, and smooth.
That smoothness is the root of most tells. The signs below are really just different symptoms of the same underlying thing — text that was optimized for plausibility rather than lived experience.
Sign 1: Uniform, Even Rhythm
Human sentences vary. We write a long, winding thought and then a short one. We start with "And" sometimes. AI writing often has an unnervingly even rhythm — sentence after sentence of similar length and structure, like a hedge trimmed flat. If a paragraph feels metronomic, that's a flag.
Sign 2: Formulaic Transitions
Phrases like "Moreover," "Furthermore," "In conclusion," "It's important to note that," and "In today's fast-paced world" appear far more often in AI text than in natural human writing. They're connective tissue the model reaches for because they're statistically common. A piece dense with these transitions is worth a second look.
Sign 3: Over-Polished, Generic Phrasing
AI tends to write in a way that sounds authoritative but says little. "This multifaceted issue requires a comprehensive approach" is grammatically perfect and almost entirely empty. Human experts usually reach for specific examples, numbers, and opinions. When writing stays abstract and hedges everything, a machine may be behind it.
Sign 4: Missing Personal Voice
Real people leak into their writing. They have quirks, strong opinions, weird analogies, a specific way of being wrong. AI writing is often oddly voiceless — competent but anonymous, as if written by a very polite committee. The absence of a distinct personality is one of the more reliable signals.
Sign 5: Perfect Surface, Shallow Depth
AI rarely makes typos or grammar mistakes, but it will happily state things that are subtly wrong, invent a plausible-sounding "fact," or repeat itself with slightly different words. Flawless surface plus shaky substance — no errors but no real insight — is a classic combination.
The Honest Catch: None of This Is Proof
Here's the part most "AI detector" pitches leave out. Every sign above can appear in genuine human writing. Plenty of people write in even, formal, transition-heavy prose — non-native speakers, corporate writers, careful students. And plenty of AI text, once lightly edited by a human, sheds every tell on this list.
That's why no detector — human or automated — can give you certainty. What you can get is a reasonable estimate: a read on how likely a piece is AI-generated, based on how many of these signals stack up. A single sign means almost nothing. A dense cluster of them means something worth noticing. But "likely" is the ceiling; "proven" is not on the table.
This matters most when the stakes are real. Accusing a student, an employee, or a writer of using AI based on a hunch — or even a detector score — is risky, because false positives are common. Treat these signs as a prompt to look closer and ask questions, never as a verdict.
Want a second opinion on a piece of text?
Paste it into our free AI Text Detector for an honest, signal-based estimate of how likely it was AI-written — no fake percentages, just a transparent read.
Try the AI Text Detector →How to Use These Signs Wisely
The goal isn't to become suspicious of everything you read. It's to develop a calibrated instinct — to notice when writing has the telltale smoothness, and to weigh that against everything else you know. Context matters enormously: a polished corporate blog post is expected to sound polished; a personal message that suddenly reads like a press release is more surprising.
If you do want to check something, use a tool built to be honest about uncertainty rather than one that spits out a confident "87% AI" and calls it a day. The most trustworthy read is one that shows you the signals and lets you judge — which is exactly the philosophy behind our own detector.
The Bottom Line
AI-written text tends to be smooth, evenly paced, transition-heavy, generic, and voiceless — flawless on the surface but thin underneath. Those patterns are real and worth learning. But every one of them shows up in human writing too, and edited AI can hide them all. Spotting AI is a matter of probability, not proof: read the cluster, respect the uncertainty, and never turn a hunch into an accusation.