Guide

How to Tell If Something Was Written by AI

March 2026 · 5 min read

AI writing tools have become so common that spotting machine-generated text is now a practical skill — whether you're a teacher marking assignments, an editor reviewing submissions, or someone double-checking their own work before sending it off.

The good news is that AI models, despite their sophistication, leave consistent fingerprints. Once you know what to look for, they're hard to miss.

1. Every sentence is roughly the same length

Human writers naturally mix short punchy sentences with longer ones. We use fragments. We let a thought run on when it needs to. AI tends to produce sentences of eerily similar length — typically medium, rarely very short or very long. Read a paragraph aloud and listen for a metronomic quality. If it sounds like a newsreader, it might be AI.

2. Certain words appear constantly

There's a specific vocabulary that large language models overuse to a statistically significant degree. The most common culprits:

• Delve — humans almost never write this word
• Tapestry — used as a metaphor far more by AI than people
• Nuanced, pivotal, multifaceted — AI loves these
• It is worth noting, it is important to recognise — filler phrases that pad without adding meaning
• Furthermore, moreover, in conclusion — transitions that appear with clockwork regularity

3. No contractions

Real people write "don't", "it's", "they're". AI, unless specifically prompted otherwise, defaults to formal expanded forms: "do not", "it is", "they are". A business email with zero contractions reads stiff. An essay with zero contractions reads like a robot.

4. The structure is perfect — too perfect

AI produces well-organised writing almost by default. Introduction, three body paragraphs each with a topic sentence, conclusion. Every paragraph roughly the same length. This is the structure we're all taught in school, and humans break it constantly. AI follows it religiously.

5. No real opinions or personal experience

AI text is confident but strangely uncommitted. It presents "perspectives" and "considerations" without ever landing on a clear point of view. It hedges. It qualifies. When you ask a human to write about something they care about, specificity bleeds through — a particular memory, an unexpected analogy, an opinion stated plainly. AI produces the shape of an argument without the substance of one.

6. The vocabulary is unusually consistent

Human writers have tics — words they overuse, words they avoid, turns of phrase that recur across their work. AI vocabulary is more uniform. It doesn't have favourites in the same way. The writing feels professionally edited even in casual contexts.

What to do if you suspect AI

Reading for these signals takes practice. A faster approach is to run the text through a dedicated detector that scores each of these dimensions automatically and flags the specific passages most likely to have been machine-generated.