Free AI Detector (+ Guide)

What is an AI detector?

An AI detector is a tool that looks for the patterns AI writing leaves behind and scores how strongly a text shows them.

AI models pick the safest next word, so their writing repeats the same habits: stock vocabulary, lists of three, balanced sentences and tidy summaries. A detector counts those habits.

How to use the AI detector

It takes a few seconds:

The screenshot below marks two things:

1. The AI score: 88 out of 100 for an AI-written LinkedIn post.
2. A tell: "Here's the thing", one of the seven phrases marked in the text.

How this AI detector works

It reads your text against a list of AI writing patterns, from single words to the shape of whole paragraphs. Each tell found adds points, weighted by how strongly it signals AI.

The points per 1,000 words become the score. 0 means no tells were found, and the band tells you what the number means in plain words.

It's the same engine as my AI slop checker, which shows the same tells with a "reads human" score instead.

How accurate is it?

To see how far to trust it, I tested it on 100 paragraphs.

Half came from my own posts written from 2013 to 2021, before ChatGPT existed. The other half came from an AI, asked for a paragraph on each of the same titles.

The test has limits. It used one AI model and plain prompts, on short English paragraphs. An AI told to sound human, or edited by a person, slips through more often.

So a high score means a text leans on AI habits, and a low one means it doesn't. Neither can say who typed it.

A real example: an AI paragraph and one of mine

Here's how the two ends of my test look in the checker. First, the start of the AI paragraph with the highest score, written for a post on hosting virtual conferences:

It scored 81 out of 100, with 13 tells marked. Most were AI vocabulary like "robust" and "seamlessly", and lists of three.

Then a line from my own post in 2014, about my first year of blogging:

That paragraph scored 0. It's uneven, personal and a little rough, which is how people write.

Why no AI detector is proof

Even OpenAI pulled its own detector. Its page says: "As of July 20, 2023, the AI classifier is no longer available due to its low rate of accuracy."

On OpenAI's own test, it caught 26% of AI text and wrongly flagged 9% of human text.

Detectors can also be unfair. A Stanford study, GPT detectors are biased against non-native English writers, found that "these detectors consistently misclassify non-native English writing samples as AI-generated."

That one matters to me: English isn't my first language, and my 2014 paragraph above scored 0. Still, treat any score as a reason to read closer, never as a verdict.

When AI writing is fine, and when it isn't

AI is fine as a starting point you then make yours: a first draft, an outline, a summary of your own notes. I use it that way.

It's a problem when the rules say no, like a class or a contest that bans it. It's also a problem when it replaces what only you know, like your experience, your examples and your opinions.

How to make AI writing read human

The tells the checker marks are the ones to fix first. These help the most:

• Add what only you know – a number from your work, a name, a mistake you made.
• Cut the stock words – "robust", "seamless" and friends rarely say anything.
• Break the rhythm – vary sentence length, and drop lists of three you didn't need.
• Say it plainly – lead with the point instead of building up to it.

Or press Humanize it, which rewrites the text with every fact kept. The AI humanizer does the same on its own page.

Who is the AI detector for?

It's for anyone who needs to know how a text reads:

• AI humanizer – writers whose draft reads like AI
• AI slop checker – editors who want every tell explained
• Paraphrasing tool – anyone rewriting a text in new words
• Readability checker – teachers checking how hard a text reads

And if you write with AI yourself, check your drafts before anyone else does.