Nowadays, AI content is being used everywhere. While there is nothing inherently wrong with AI content, there are certain ethical concerns that arise in academic and work-related situations.

For example, students, even when prohibited, use AI content to get out of doing their own work. Unscrupulous writers can try to fool their clients by passing off AI content as their own.

In these types of situations, people use AI content detectors to make sure they aren’t being duped. If you’ve ever used these tools yourself and wondered how they work, today’s the day your question will be answered.

In this post, we’re going to dive deep into how these tools work so that you can appreciate what goes on in the background when you click on the “Check AI” button.

What are AI Content Detectors?

First of all, let’s clear up what AI content detectors actually are.

AI content detectors are tools that check a given piece of content and tell if it is written by a human or generated using an AI tool. These detectors check a number of factors and elements in the given content to determine its origin (more on those later).

Many online AI detectors can tell if a certain part of the content is AI, while the rest is human-written. These tools are made to catch content created using ChatGPT, Google Gemini, Claude AI, and other similar tools.

Later on in this post, we’ll talk about how well these tools work and how accurate they are.

For now, however, let’s move on to their functionality.

How do AI Content Detectors Work?

AI content detectors work by checking various elements in the provided content. If the elements indicate patterns of AI content writing, the content is declared to be AI-generated.

These tools are trained to detect AI content from human content. When they are developed, their AI engine is given pieces of AI content along with pieces of human-written content. The engine is able to see the differences and learn (via machine learning) how to distinguish between them.

What Elements and Factors Do AI Content Detectors Look for?

Moving on, let’s take a look at the elements and traits that AI content detectors look for.

Pattern consistency

One of the main things that AI detectors check is pattern consistency.

Human writing is, by its very nature, inconsistent. By that, I don’t mean that a human writer will be jumping from tone to tone or changing styles every other sentence. I mean that they will use different sentence lengths, punctuation choices (such as switching from a semicolon, a comma, or an em dash), and vocabulary throughout the content.

Take this article as an example.  Right at the beginning, you can see that the first line is short, the next one is quite long, while the next two are moderately lengthy.

On the other hand, AI doesn’t normally do this. The content generated by AI tools is mechanically consistent and “symmetrical.”

In the screenshot below, you can see this in action. ChatGPT created some content of about 200 words. Two sentences were exactly 30 words in length, spaced about a paragraph apart. Two sentences were exactly 14 words, similarly spaced. Two sentences were exactly 20 words. The other sentences were around 17, 16, and 19 words.

Tone and style

AI detectors also check the tone and style of the content.

Nowadays, AI tools have evolved enough to use a conversational tone in their content. The text doesn’t have a lifeless look to it, as one might have expected a decade ago from the early tools.

However, there is still a difference between the tones used by a human and an AI generator. By default, AI tools usually have a formal and rigid tone in their content that stands out. Even when instructed to be humorous, they might generate content that looks awkward and forced. 

Repetition of words and phrases

The repetition of words and phrases in the content is also a major tell as to whether it’s AI-generated or not.

As previously mentioned in the “pattern consistency” part, there is usually an inconsistency in the words that a human uses in their content. Take the word “symmetrical” in this article. I’ve used it once, a few paragraphs above. You won’t find it anywhere else. Same with the words “prohibited” and “rigid,” etc. I used them once, and that’s it.

But AI usually doesn’t do this. It will repeat words and phrases in a noticeable way. Here, in this screenshot, you can see ChatGPT doing the exact thing: (This is a minor example in a short piece of content. The longer the content gets, the more apparent it becomes.)

As you can see, the words “become increasingly” are mentioned twice with the same type of progression preceding them. In the first paragraph, the words “As artificial intelligence continues to evolve…” precede the phrase “become increasingly,” while in the last paragraph, the words “as generative models grow more sophisticated…” precede the phrase “becomes increasingly.” It’s a linguistic repetition that, while not harmful to the quality of the content, indicates the AI origins of the same.

Predictability

Predictability is another factor that sets AI content apart from the rest. In AI writing, you’ll find that each word that follows the next is very predictable. It is the most normal word that you would find in the progression. For example, AI could give a definition as follows:

ML stands for machine learning. It is the branch of computer science in which a computer system is equipped to learn from the values it interacts with in the form of inputs, outputs, user settings, etc.

Here, when you start reading the definition, you know that the most normal thing for an acronym to be followed by is “stands for.” You know that once the acronym is described, the next thing is a definition that starts with “it is” or “it refers to.”

And that is exactly how the text is created.

On the other hand, a human could write the same definition in this way:

ML, the technology you’ve seen blared about all over the online world recently, stands for machine learning. It has to do with making computers and software programs learn stuff on their own.

This definition isn’t predictable. It starts with a little twist (the “blared about” part) and then goes into a slightly informal dip by using the word “stuff.” This is what a human would do when writing a casual blog or article.

Topic consistency

Topic consistency is another indicator of AI content. AI generators stick to the given topic with pinpoint accuracy without moving an inch. They will stay very relevant and not deviate at all from the main point.

Humans, on the other hand, will naturally stray a little here and there. For example, a human writer may introduce an analogy that may be completely different from the topic at hand.

Are AI Content Detectors Accurate?

Here is the ugly truth.

Most AI content detectors are not accurate. I’m not just saying this as an opinion or a cynical speculation. I’ve been writing since 2019. I’ve used a lot of AI tools and a lot of AI checkers. Most of them don’t work very well and are terrible at detecting AI content.

They can flag human content as AI and AI as human. A notorious example of such tools is ZeroGPT. It is very popular online, but it is shockingly poor in performance. I’ve had to deal with people who use it to check for AI and tell me that my human-written content is, in fact, AI. This tool has perhaps an accuracy of 10%.

However, there are some excellent tools on the internet as well. We will mention them in the next heading. These tools, contrary to the lame ones, are accurate around 80% of the time.

To answer the question: AI detectors are fairly accurate as long as you pick the right tools, which are quite few. Even with the good tools, it’s not advisable to fully depend on their outcome. You should manually check the content before making up your mind.

Top Tools to Consider in 2025

Copyleaks AI Detector

The AI detector by Copyleaks has a good reputation online, and for good reason. It works reasonably accurately and is free to use. It highlights specific parts in the content that it finds to be AI-generated. Copyleaks also works quite quickly and has no annoying signup requirements.

Of course, it’s not perfect. It does have some issues with accuracy. Sometimes, the inclusion or exclusion of a title in the content can cause the tool to vacillate between “AI content detected” or “Human written.” This is a specific issue that I faced when I used it.    

Grammarly AI Detector

The AI detector by Grammarly is also quite accurate. I’ve used it many times. Most of the time, it would correctly label my content as human-written. A few times, it would highlight a couple of sentences incorrectly and tell me they were AI.

The AI checker is available for free on Grammarly’s website. You can enter up to 10,000 characters at one time. The checking process is quite fast.

If you have Grammarly installed as an extension on your device or browser, you can use the AI checker on it as well. 

GPTZero

This tool shouldn’t be mistaken for the infamous ZeroGPT. This one is GPTZero, a different platform. It is a free tool that provides accurate results. It does have an annoying 5,000-character limit, but it makes up for it by providing a writing improvement and “Check Bibliography” feature right beside the AI checker.

Conclusion

And with that, we’re going to wrap this article up.

To sum up, AI content detectors work by looking for various patterns and elements in the given content. They have been trained to detect the consistencies, vocabulary, and tone, etc., that are usually found in AI content. If the given content looks similar to AI content in terms of these elements, it is branded as AI; otherwise, it is not.

Not all AI checking tools are accurate. Some of them are quite bad and have almost no reliability. Some of them, on the other hand, aren’t half bad. We’ve listed three choices that you can try out.