What’s the Point of AI Detectors?

We’ve just released our new AI content detector. It’s live in Page Inspect in Site Explorer. You can test it for yourself.

I was previously a skeptic of AI content detectors, and many people still are. Andrew Holland recently shared a LinkedIn comment that does a good job summarizing common concerns:

In a nutshell:

AI content detectors are not accurate. AI content detectors are punitive tools.AI content detectors aren’t helpful.

These are valid concerns, so I wanted to talk through them, one by one, and explain why AI detectors are a useful tool in a world where 74% of new content is created with the aid of generative AI.

I’ve tested many AI detectors and seen them incorrectly flag my skilled, human work as “AI-generated”. And you’ve probably seen occasions where the Declaration of Independence, or a famous speech, or passages from The Bible were confidently (and very incorrectly) labelled as AI-generated.

But in the academic literature, AI detectors routinely hit 80% (or greater) successful detection rates. OpenAI reports detecting text generated by its models with 99.9% accuracy.

Here’s an example of our AI detector nailing content detection, correctly identifying the sections of Patrick’s article generated with GPT-4o:

And another example from one of my hobby websites, where the model correctly recognises that I used one of Meta’s Llama models to write the article:

These are not random guesses. This is accurate detection. So what explains the apparent gap between the theory and the practice? How can AI detectors be so wrong, and so right, at the same time?

“Famous” text is usually in AI data sets. Many of the most egregious examples of AI detectors getting it wrong are actually expected behaviour. Famous texts are usually found in LLM training data, shaping the writing patterns that AI detectors look for, and causing a false positive. As Mark Williams-Cook explained on LinkedIn, flagging a famous political speech as AI-generated “…is the correct answer when you build a tool to identify the output of a corpus of training data, but then you choose to feed it part of the training data.”Many free AI detectors are overhyped. Many free AI detectors are just basic API calls that are little better than random number generators. Effective detection requires fine-tuned detection models and regular updates to keep up with new model releases. This is difficult and expensive to achieve, and most free tools don’t attempt it.AI detectors are easy to misuse. Most detection models perform best when they’re used on the same type of content they were trained on. AI text is much harder to detect when it’s “humanized”, or when documents content a blend of human-written and AI-generated text. These are well-known limitations, but they aren’t often communicated to users.There are not always clear answers. As writing workflows incorporate AI in more subtle, nuanced ways, it becomes harder to answer the question “is this AI-generated?” Is something AI-generated if it was written by a human but copyedited by AI? Or outlined by AI but written by a human? These are increasingly blurry lines.

Like LLMs, AI detectors are statistical models. They deal in probabilities, not certainty. They can be incredibly accurate, but they always carry the risk of false positives.

If you understand these limitations, false positives don’t need to be problematic. Don’t weigh any single result too heavily. Run many tests and see how the results trend. Combine the results with other forms of evidence.

But many AI detectors are marketed as infallible truth-telling machines. That creates false expectations and encourages them to be used in bad ways that don’t reflect how they actually work. Which brings us to the second objection…

We’ve all heard of students being flunked because of AI detectors, or freelance writers losing contracts because their work was incorrectly deemed to be AI-generated. These are real problems caused by the misuse of AI detectors.

It’s worth stating concretely: no AI detector should be used to make life-or-death decisions about someone’s career or academic standing. This is a bad use of the technology and misunderstands how these tools function.

But I don’t think the solution to these problems is to abandon AI content detection wholesale.

There is a real and pressing demand for these tools. As I write, “ai detector” is searched 2.5 million times per month, and demand has been growing rapidly. As long as we can generate text with AI, there will be utility in identifying it.

Education is a better answer. People building and promoting AI content detectors need to help users understand the constraints of their tools. We need to encourage smarter use, following some basic guidelines:

Try to learn as much about the detector’s training data as possible, and use models trained on material similar to what you want to test.Test multiple documents from the same author. A student’s essay was flagged as AI-generated? Run all their past work through the same tool to get a better sense of their base rate.Never use AI content detectors to make decisions that will impact someone’s career or academic standing. Always use their results in conjunction with other forms of evidence.Use with a good dose of skepticism. No AI detector is 100% accurate. There will always be false positives.

There are many bad, silly ways to use AI detectors, but there are also many good use cases. Which brings me to the final objection…

Generative AI is embedded natively in Google Docs, Gmail, LinkedIn, Google Search. AI text is being woven inextricably through the fabric of the internet. It’s already a fact of life, so why bother even trying to detect it?

There’s real truth to this. Our AI detector estimates that 74% of new pages published in April 2025 contained some amount of AI-generated text. This number will only grow over time.

I’ve used the analogy of post-nuclear steel before. Since the detonation of the first nuclear bombs, every piece of steel manufactured has been “tainted” by nuclear fallout. It’s not hard to imagine a world where every piece of content is similarly “tainted” by AI output.

But this, to me, is the biggest justification for using an AI detector. The entire internet is being swamped with LLM outputs, so we need to understand as much as possible about the tools and techniques that shape the content we interact with every day.

I want to know…

Which AI models are the best for creating high-quality content.How often my competitors publish AI content, and which models they use.How easy it is for other companies (like Google) to detect our AI content.How much AI content is present in a particular SERP, and how much effort I need to invest to rank.How organic performance metrics correlate with different levels of AI use, like search traffic, keyword rankings, and backlinks (as I type, we’re running a study on this).

The goal of AI content detection isn’t making black-and-white moral judgements about AI use: this is AI content, so it’s bad; this is human content, so it’s good. AI can be used to make excellent content (if you’ve read the Ahrefs blog recently, you’ve been reading content that contains AI-generated text).

The goal is to understand what works well, and what doesn’t; to collect data that offers some advantage and helps improve the growth of your website and your business.

Final thoughts

Most of the new content on the web is created with the aid of generative AI. Personally, I want as much information about that AI as I can get my hands on.

Our new AI detector is live now in Site Explorer. You can test it for yourself, run experiments, and begin to understand the impact generative AI is having on online visibility.