5 Best Free AI Detectors (+ Why You Don’t Need Any of Them)

I’m thinking you’re here looking for the best free AI detectors. Well, you’re in luck. We’ve compiled a comprehensive review of all the “top” AI detection tools on the market today based on our own testing… and in the process, we’ve concluded that none of them are reliable. And I mean none. Like zero.

There’s a lot of misunderstanding and confusion out there about AI detectors… and as AI builders ourselves, we want to clear this up. We’re going to take you through what people claim to be the best free AI detectors out there, showing what they can and can’t do. As I’ve said, they can’t consistently do that much.

🔑 AI detectors don’t really work. More specifically, they’ve been shown to be consistently unreliable by many studies (including tests from OpenAI, the makers of ChatGPT). They often mistake human written content for AI-generated content, and vice versa.

More importantly, Google has openly encouraged using AI in the content creation process. In a tweet they shared, “Use Gemini to help optimize SEO and boost your online presence to grow your small business.”

Unless you’re looking for free AI detectors to help make sure your students aren’t using too much AI for their scholastic works (or if you’re a student trying to toe that line), there’s really not a compelling reason to care about whether or not your content is created with the help of AI… as long as it’s genuinely good and delivers value to your audience.

We wanted this to be as unbiased an experiment as possible, so we’ve tested out each of these best AI detector tools, using the same 6 pieces of content… I’ll get into how we did that in a moment.

After running through the results of how each of these AI detectors performed, we’re also going to look at why AI detection is such a tricky concept, and how it can create issues for both businesses and content creators.

How We Tested the Free AI Detectors

The big question here is… can you detect AI-generated content? The short answer is no, at least not reliably. And for most use cases we come across, it doesn’t really matter if AI is used in the creation process, as long as the end result is clearly useful content for real people.

🔑 We believe AI detectors do not work today. OpenAI (the makers of ChatGPT) have also found in their testing that AI detectors are unreliable at best:

When OpenAI tried to train its own detector, the company found it labeled human-written text like Shakespeare and the Declaration of Independence as AI-generated.

A quick timing note: we ran this hands-on experiment in October 2024, using AI text generated with the models available back then. Models and detectors have both evolved since, but the reliability problem hasn’t gone anywhere. In December 2025, an NPR report cited research showing Turnitin, GPTZero, and Copyleaks flagging human-written work as AI, and a teacher whose own PhD dissertation chapter scored roughly 90% AI in GPTZero.

AI companies have also started watermarking text since our test. Google marks AI text from its products with SynthID, Anthropic is adding a watermark to new Claude models, and OpenAI is rolling one out for ChatGPT in the EU. Each provider checks its own mark, so none of this makes the third-party detectors below more reliable. We cover how it works in our guide to AI text watermarks and SEO.

Before we dig too deep into this, let me share how we evaluated these popular free AI detectors. For each AI detector tool, we used 6 pieces of content, so 2 each from all the following categories:

1. Content written entirely by humans, to test how well the detectors recognize human writing.
2. Content generated entirely by AI, to test how accurately they catch it.
3. AI-generated content that a human then edited, to see how they handle a mix of both.

Here’s a breakdown of the content we used for this free AI detectors review & experiment.

Human-Generated Content Samples

We used these paragraphs from my friend Ali Luke’s guest post 13 Best Mom Blogs to Follow, written over on my blog, RyRob.com, before AI tools emerged onto the scene:

Clean Mama is a mom blog by Becky Rapinchuk, centered around a cleaning system to help moms keep their homes clean and under control. It’s aimed at busy moms who want a clean, relaxing home … without having to spend hours getting it that way.

As well as offering a bunch of free printables as email sign-up incentives, Clean Mama monetizes through a Homekeeping Planner, various downloadable PDFs, and cleaning products. You’ll also spot affiliate links (particularly for Amazon).

We also used this excerpt from my post What is WordPress?, which I first published many years ago, long before AI tools were in use:

A self-hosted WordPress.org blog gives you the freedom to use as many themes and plugins as you’d like. You also have the ability to monetize your website without restrictions and without paying a higher premium to your monthly hosting provider.

WordPress.com’s higher-priced plans do offer more customization abilities, but the cost is much higher than running a self-hosted WordPress.org site on Bluehost.

A self-hosted WordPress.org install gives you complete control to do what you want with your website, with very few restrictions. You can hire a website developer to build custom functionality, use third-party plugins and themes, monetize your website, create your own themes, and basically do anything you could ever want.

100% AI-Generated Content Samples

To come up with our AI-generated content samples, we created some text using RightBlogger’s Article Writer tool.

Here’s our first entirely AI-generated example, from a post about “camping in the rain”:

Who says a little rain has to ruin your camping trip? Embracing the elements can actually make for a unique and memorable adventure. Camping in the rain presents its own set of challenges, but with the right preparation, it can be an enjoyable experience rather than a soggy mess. You’ll find that the sound of rain on your tent can be soothing, and the misty atmosphere adds a magical touch to the wilderness.

This post will explore essential tips and tricks to help you stay dry, warm, and comfortable while camping in wet weather. From choosing the right gear to setting up your campsite, we’ll cover everything you need to turn a rainy weekend into an unforgettable outdoor adventure. So, pack your rain gear and let’s get started!

And here’s a second example, again fully AI-written, from a post we created using RightBlogger, on the topic of WordPress plugins:

At its core, a WordPress plugin is a piece of software you add to your WordPress site to improve its functionality. Think of it as an app on your smartphone. Just as apps let you customize your phone with everything from games to productivity tools, plugins let you tailor your website.

When you install a plugin, it integrates with your WordPress installation, offering new features or enhancing existing ones. They vary widely in what they offer, from simple tweaks to complex systems, and can be free or come with a price tag. But the main takeaway? They allow you to do more without needing to be a tech expert.

AI-Generated & Human Edited Content Samples (Hybrid)

What about AI-generated content that’s been edited by a human? We were really curious how the free AI detectors would handle this scenario. Here are the excerpts we used for that part of the experiment. Again, each of these pieces were written by AI first… and then hand-edited by us to sound more ‘human’ and how we’d naturally write here on this blog.

Here’s part of an AI-generated, human-edited piece on “how to bake a cake”:

There’s a cake for every occasion out there … and a cake to suit every taste! Here are three great options:

• Sponge Cakes: Light and fluffy, these are the go-to for layered cakes. This type of cake is perfect for soaking up syrups.
• Chocolate Cakes: Great chocolate cakes are rich, moist, and full of chocolatey goodness (and they’re my personal favorite).
• Pound Cakes: Dense and buttery, these cakes are perfect on their own or can be dressed up with glazes or fruit.

And here are some human-edited paragraphs on a separate piece about “training for a marathon”:

A marathon is a total of 26.2 miles … and that kind of distance takes endurance and grit.

Running a marathon demands more than just physical strength, it requires true mental fortitude that lets you push through fatigue and doubt. Every single mile tests your ability to keep on going and fight the urge to quit.

A good marathon training plan helps you build the physical and mental endurance you need to tackle a full marathon.

Success Criteria: What Counts as Accurate?

To count an AI detector as “accurate” for these tests, we were looking to hit the following criteria for each of our 3 content types:

• For the human-written pieces: 75% or more confidence that the piece was human-written.
• For the AI-written pieces: 75% or more confidence that the piece was AI-written.
• For the hybrid pieces (first drafts from RightBlogger’s Article Writer that we then edited by hand): a score between 25% and 75% either way, or a result that detects a good mix of human and AI content. We didn’t expect strong scores in either direction here, given the mix of AI and human input.

🔑 We found that these “best” free AI detectors we tested varied wildly in whether they could detect AI-written content or not… in any of these 3 scenarios.

When it came to human-edited AI-generated content, the AI detectors were often completely inconsistent in whether they thought the content was highly likely to be AI or highly likely to be human (we expected middle of the road scores for AI vs human on those pieces).

The other results were crazy too… which brings us to the most important question we landed on after running these experiments…

Should I Use an AI Detector Tool?

No. Probably not, but it depends a little bit on your use case.

If you’re assessing students’ work, then it might make sense to ban the use of generative AI, we get that one. An argument we’ll leave for another day, is whether even that fight is one worth having, given where the march of history is pointing right now.

Just beware though, that even the best free AI detectors on the market today may incorrectly flag human-written text, potentially leading to students being unfairly penalized… so it’s important to proceed with caution.

Most likely, you’re considering using AI detector tools because you hire freelancers, and you want their work to be fully original, or because you’re concerned that your own AI-generated content may not be good enough.

But is AI really an issue here? That’s the real question underneath all of this.

🔑 Here’s my take on AI detection: it isn’t reliable, and it’s pointless for businesses. What your readers care about (and what Google cares about!) is whether your content is useful, relevant, and accurate. How exactly that content was produced, simply doesn’t matter.

We’ll probably keep looking back and scratching our heads, wondering why we ever cared about AI detection (for most use cases).

Here’s what Google says about AI in its official guidance on AI-generated content (published February 2023): “Automation has long been used to generate helpful content, such as sports scores, weather forecasts, and transcripts. AI has the ability to power new levels of expression and creativity, and to serve as a critical tool to help people create great content for the web. […] However content is produced, those seeking success in Google Search should be looking to produce original, high-quality, people-first content demonstrating qualities E-E-A-T.”

It’s fine for you (or a freelancer you’ve hired) to use AI to help create great content. That content still needs to be high quality, as it always has. Google’s current guidance on generative AI content adds one caveat: using AI to generate many pages without adding value for users may violate its spam policy on scaled content abuse.

If a freelancer can produce an amazing piece for you with the use of tools like RightBlogger or ChatGPT, that piece is just as good as one where every word was typed by hand.

Plus, AI detectors may incorrectly flag 100% human-written text as being AI produced… much to the frustration of freelancers and clients alike. As one anonymous freelancer wrote on Reddit:

During the editing process, a sample of my original work was flagged with “90% confidence this passage was generated by AI” when I did not use chat GPT or any other services in my work, and I’m now forced to revise the false positives.

If you still wanna go ahead and use free AI detectors, though, I’m still on your team. I don’t have to agree with your take in order to say that I support you on your content journey, regardless.

So, let’s take a look at the most popular free AI detectors on the market today, and see how they did in our experiment to figure out how accurate these tools really are.

5 Best Free AI Detectors (Comparison Chart)

Here’s a quick look at how the best free AI detectors out there performed in our experiment. (Note that the free plan for many of these is very limited, which is another big red flag about using these tools, in my book.)

	Test Score	Features	Free tier	Paid from (billed annually)
GPTZero	67%	AI detection, plagiarism checking, Google Docs and Chrome extension	10,000 words/month	$12.99/month
Originality	50%	AI detection, readability score, and plagiarism check	Limited free scans	$12.95/month
Copyleaks	50%	AI content detection and cross-language plagiarism checker	25,000 characters per scan, no login	$13.99/month
Undetectable AI	50%	AI detection, AI humanizer, Chrome extension	Free on-site detector	$5/month
Sapling	33%	AI detection, Autocomplete Everywhere, and writing assistance	2,000 characters per check	$12/month

Now, let’s get into the nitty gritty specifics of how each of these free AI detectors performed in our test.

5 Best AI Detectors: A Comprehensive Review

Here are our top picks for the best AI content detectors (even though you don’t need them lol):

1. GPTZero

First off, GPTZero performed the best in our AI detection test. This tool is an artificial intelligence detection software that seeks to help you identify artificially generated text, especially if it is produced by large language models such as ChatGPT, Claude, Grok, and Gemini.

GPTZero first became known for scoring text on “perplexity” (how predictable the word choices are) and “burstiness” (how much the sentences vary), since human writing tends to be less uniform than AI text. Today it describes its detector as an end-to-end deep learning model with a sentence-by-sentence classifier, trained on human writing and on text from a range of LLMs.

This AI detector tool then highlights sentences where AI-generated content is detected, providing detailed explanations for the detection. This feature attempts to help you understand the results and make what they believe are necessary adjustments.

Accuracy of the GPTZero AI Detector

How GPTZero did in our test (spoiler, it did best):

✔️ Identified our first human-written piece as 99% likely to be human-written.
✔️ Identified our second human-written piece as 98% likely to be human-written.
✔️ Identified our first AI piece as 100% likely to be AI-written.
❌ Identified our second AI piece as 70% likely to be human-written.
✔️ Identified our first AI-generated, human-edited piece as 61% likely to be entirely human-written, 39% likely to be entirely AI-written (0% mixed).
❌ Identified our second AI-generated, human-edited piece as 86% likely to be human written, 14% likely to be AI-written (0% mixed).

Other Features of GPTZero

• GPTZero says its detection model has seven components that process text in a multi-step approach, aimed at accurate predictions with as few false positives as possible.
• Its Chrome extension checks text inside Google Docs and across the web (the free plan includes 5 AI highlights). The Professional plan adds LMS integration with classroom apps like Canvas and Google Classroom.

Pricing for GPTZero

Paid plans start at Premium for $23.99/month ($12.99/month billed annually) with 300,000 words/month. Professional is $45.99/month ($24.99/month billed annually) with 500,000 words/month. Official limits: GPTZero pricing.

The free plan lets you scan up to 10,000 words/month and has limited features.

2. Originality.ai

Originality.ai attempts to verify the authenticity of content by using AI to help distinguish between human-written and AI-generated text. It offers a wide range of features, including AI detection and plagiarism checking, while hoping to convince you this is the way to “maintain the integrity of your web content.”

They position this tool largely for writers, pitching that you can run your content through it before submitting it to your client, providing “peace of mind and credibility” in your work.

While this tool also proved to be mostly inaccurate, flagging your content as AI-generated might indicate that you do need to work a bit more on your tone or word choices. That could in fact be a good thing if it helps you avoid unnecessary rounds of edits, back-and-forth conversations, or disappointment with your clients.

Accuracy of Originality.ai’s AI Detector

Originality.ai’s test results:

✔️ Identified our first human-written piece as 99% likely to be human-written.
❌ Misidentified our second human-written piece as 89% likely to be AI-written.
✔️ Identified our first AI piece as 100% likely to be AI-written.
✔️ Identified our second AI piece as 98% likely to be AI-written.
❌ Misidentified our first AI-generated, human-edited piece as 92% likely to be fully AI-written.
❌ Misidentified our second AI-generated, human-edited piece as 91% likely to be fully human-written.

Originality.ai claims to be 99% accurate, but in our tests, it identified a fully human-written piece as AI-written with a high degree of confidence. That’s a really big problem for writers who submit content to clients & are subjected to arbitrary edit requests based purely on the results of this free AI detector.

This AI detector was also very inconsistent about the AI-generated, human-edited pieces (which both went through a similar level of editing). One was detected as highly likely to be fully AI-written, whereas the other was considered highly likely to be fully human-written. Again, inconsistent.

Other Features of Originality.ai

• The Fact & AI Hallucination Checker flags statements that may be wrong and links sources so you can check them. This can help reduce AI “hallucinations”… though keep in mind that the fact checker uses AI itself, so its answers need checking too. lol
• A plagiarism checker shows whether content is fully original or whether sections have been copied-and-pasted from elsewhere. I like this feature.
• The Readability Checker gives your content a readability score. This is helpful if you want to make sure your content is easy for your audience to understand, another good feature.

Pricing for Originality.ai

Originality.ai has a free plan for limited use, and you can run a free AI scan right on its homepage.

After that, Originality.ai’s paid plans start at $14.95/month ($12.95/month billed annually), which includes 2,000 credits. Each credit covers 100 words, so that’s up to 200,000 words of scanning per month. You’ll also get access to additional features like plagiarism scanning, readability scanning, and a 30 day scan history.

While Originality.ai fails the reliability test as an AI detection tool in my book, some of their other features help make it somewhat useful for writers with other editing needs.

3. Copyleaks

Copyleaks bills themselves as an advanced platform (powered by AI) to help you detect both plagiarized and AI-generated content. This platform has several tools, each claiming to be “effective on their own, but even more impactful when combined.”

Their range of tools include:

• AI-based text analysis that flags potential plagiarism, multiple forms of paraphrasing, copyright infringement, and more. These features can actually be pretty useful.
• AI content detection that they claim works in 30+ languages, including English, Spanish, French, Chinese (Traditional and Simplified), and more. We’re not convinced.

Accuracy of the Copyleaks AI Detector

Copyleaks claims to be “the most accurate AI content detector and ChatGPT checker.” We put it to the test and the results, while mixed, might support their claim to being the best AI detector in terms of accuracy, but it still failed our experiment, it’s also an unreliable tool in our experience.

Copyleaks test results:

✔️ Identified our first human-written piece as 100% likely to be human-written.
✔️ Identified our second human-written piece as 100% likely to be human-written.
✔️ Identified our first AI piece as 100% likely to be AI-written.
❌ Misidentified our second AI piece as 100% likely to be fully human-written.
❌ Misidentified our first AI-generated, human-edited piece as 100% likely to be fully human-written.
❌ Misidentified our second AI-generated, human-edited piece as 100% likely to be fully human-written.

Note: For what it’s worth, I found it strange that this free AI detector reported 100% confidence in all its ‘decisions,’ including the misidentifications where it was wrong.

Other Features of Copyleaks

• Plagiarism detection that Copyleaks says covers 100+ languages, including matches across different languages.
• Source code scanning: as well as checking text, Copyleaks says it can spot AI-generated code, code plagiarism, and licensing problems.

Pricing for Copyleaks

Copyleaks Personal still bundles AI detection and plagiarism checking: $16.99/month (100 unified credits ≈ 25,000 words) or $13.99/month billed annually (1,200 unified credits ≈ 300,000 words). One credit covers up to 250 words, and the Pro plan for small teams starts at $74.99/month billed annually. See Copyleaks pricing for current allotments.

For free, the Copyleaks AI Detector scans up to 25,000 characters without logging in, and a free account adds more monthly credits.

4. Undetectable AI

Undetectable AI was built with the purpose of detecting AI-written text and helping to make your AI-generated content sound “more human.” They claim to use a variety of machine learning algorithms to analyze text and identify potential AI-generated content.

What makes this tool unique in the space, is that it tries to help make AI-generated content sound more human, by incorporating natural language processing techniques to create content that they claim won’t be as easily detected as AI-generated. An interesting little spin that I’m not against.

Accuracy of Undetectable AI

Undetectable AI’s test results:

✔️ Identified our first human-written piece as 100% likely to be human written.
❌ Misidentified our second human-written piece as 87.5% likely to be AI-generated.
✔️ Identified our first AI piece as 87.5% likely to be AI-written.
✔️ Identified our second AI piece as 87.5% likely to be AI-written.
❌ Misidentified our first AI-generated, human-edited piece as 87.5% likely to be fully AI-written.
❌ Misidentified our second AI-generated, human-edited piece as 87.5% likely to be fully AI-written.

Note: When we ran our test, Undetectable AI didn’t give precise percentages. It showed results from 8 AI tools with a 100%, 50%, or 0% AI rating for each, so we calculated the percentages ourselves.

Other Features of Undetectable AI

• Beyond the text detector, Undetectable AI now offers an AI Image Detector and an AI Humanizer that rewrites stiff text.
• Its Chrome extension puts these tools in your browser, so you can use this (not entirely reliable) detector on the fly.

Pricing for Undetectable AI

Undetectable AI’s monthly plans start at $19/month for 20,000 words/month of humanizing credits. Annual plans start at $5/month ($60/year) for 10,000 words/month. AI detection itself is unlimited on paid plans. See current tiers on Undetectable AI pricing. They seem to be moving in the direction of creating human-sounding AI-generated content, which in my opinion, is a better move than this whole AI detection thing.

For free, you can paste up to 10,000 words at a time into their on-site AI detector.

5. Sapling

Primarily designed to help teams communicate more efficiently and effectively with their clients and customers, Sapling’s AI Detector attempts to identify AI-generated content by examining text through a combination of linguistic analysis, contextual understanding, and advanced machine learning algorithms.

It looks for specific patterns and features typical of AI-generated text, which are often more consistent and predictable than human writing.

Their AI detector also evaluates the context and depth of the text, recognizing that human writers draw on a wide range of experiences, resulting in more natural and relevant content. Sounds pretty good, but how did they do?

Accuracy of Sapling’s AI Detector

Sapling.ai’s test results:

❌ Misidentified our first human-written piece as 100% likely to be AI-written.
❌ Misidentified our second human-written piece as 99.7% likely to be AI-written.
✔️ Identified our first AI piece as 100% likely to be AI-written.
✔️ Identified our second AI piece as 100% likely to be AI-written.
❌ Misidentified our first AI-generated, human-edited piece as 100% likely to be fully AI-written.
❌ Misidentified our second AI-generated, human-edited piece as 100% likely to be fully human written.

Note: Sapling didn’t have much nuance in their testing. It thought text was either extremely likely to be AI or extremely likely to be human-written, with virtually no middle ground. With the AI-generated, human-edited pieces, it was equally confident in completely opposite directions.

Other Features of Sapling

• Autocomplete Everywhere, a Pro feature, gives deep learning-powered predictive text suggestions across popular CRM and messaging platforms. If you work in a customer-facing role, it can speed up your replies. This is a better use case for their tools.
• Sapling also has an AI-powered grammar checker so you can catch any errors in your (human-written!) pieces. This performs much better than their AI checker.

Pricing for Sapling

Sapling offers a forever-free plan with AI detector checks of up to 2,000 characters each. The Pro plan costs $25/month ($12/month billed annually) and raises that to 100,000 characters per check.

My Final Thoughts on AI Detectors

Like I mentioned earlier, my take on AI detectors is that they’re not worth using. They’re all inconsistent. You can see this is backed up by the results of our experiment above.

AI detectors simply aren’t reliable. So what’s the point in using them?

Some of these AI detectors did a good job spotting our AI-generated text. But they also made mistakes and sometimes flagged human-written content as highly likely to be written by an AI. The latter is a much bigger problem.

These AI detectors also often showed 100% certainty… even when they were wrong. Another really big problem with using these tools.

Ultimately, you need to ask yourself why you’re considering using an AI detector at all. Seek to understand which problem(s) you actually have.

• If you want top-notch written content for your site, then does it really matter whether it’s produced with the help of AI? What’s most important (and always has been) is the quality of your finished work.
• If you’re not sure you have the ability to judge how good a piece of writing is, then you need to bring on board someone with editorial expertise who can tune up your content, or give your writers useful feedback that’ll help them create the type of content you really want.

From Google’s perspective, AI is fine (in fact, Google is even using AI in search results and recommends using their Gemini generative AI tooling to create your digital content). All that matters is how strong your published content is.

Your AI-generated content doesn’t need to be bland, stilted, inaccurate, or padded out. Great, up-to-date AI tools like RightBlogger let you produce text that’s human-like, in a wide range of styles & tones (including your own brand tone).

With a little editing to humanize your AI drafts and weave in your own personal experience, stories, examples, and expertise, you (or your writers) can produce incredible, top-rank-worthy posts faster than ever. I know, because I’ve been doing it for years now.