3 Free AI Detectors for Teachers to Check Plagiarism and AI Content in 2024 (Tested)

3 Free AI Detectors for Teachers to Check Plagiarism and AI Content in 2024 (Tested)

I can totally understand the nightmare you've been dealing with since the advent of ChatGPT, Bing AI, Google Bard, and all those other AI writing tools. It must have felt like the long-standing plagiarism checking system in schools and institutions just crumbled overnight under the weight of this new menace – potential undetectable plagiarism.

It's important for students especially youth to develop their originality of thoughts, but with AI assistants churning out seemingly original content, it's become a real challenge.

Here's the good news though – in response to this escalating challenge, a myriad of AI detectors have swiftly emerged. And in this article, we'll be reviewing the best AI detectors for you awesome teachers out there.

But heads up, the existence of AI detectors doesn't mean the end of your nightmare just yet. You see, while there are many AI detectors to help detect AI-generated content, there are also many AI tools being developed for the sole purpose of fooling these very detectors. It's an arms race, really.

So, to provide some much-needed support to all our educator readers, we won't just be sharing the best FREE AI detectors in 2024 (our teachers community has tested these tools), but we'll also be equipping you with knowledge on how AI detectors actually work. That way, you'll know the right way to incorporate a much-needed layer of human proof to your students' work while using these AI detectors.

How AI Detectors Work

Is AI detector a scam or is its functionality genuine? This probably be the question of many educators including me. After looking at various researches and also my students' works, I have come up with some key points about how AI detectors work, and even can detect AI-generated content without them. Here's a breakdown of the key methods:

  1. Statistical Analysis

Perplexity - This one measures just how "out there" a piece of text really is. High perplexity equals more randomness and unpredictability - a telltale human quality. AI language models like to play it safe. Look for predictable word combinations and sentence structures when you read a piece (trust me they are really easy to identify), things like "unleash the power", "unveil the potential", "embrace the challenge", or "supercharge your journey". Not only they are very corporate-sounding but also unnatural in some contexts (why do you need to unleash the power of Emily Dickinson's I Had Been Hungry All the Years??)

Burstiness - Robots write with metronomic regularity. But us humans? We write in glorious, erratic bursts with varied lengths and tempos and with the same energy as when we sit in our car 7AM in the morning screaming before heading to work!

Statistical Patterns - AI Detectors also analyze other statistical patterns in the text, such as word frequencies, specific word choices, and grammatical structures that are typical of AI-generated content. Like us on a 11PM late night marking the students' works, AI sometimes struggle with maintaining logical coherence and flow over longer passages.

Of course, no AI detector is infallible. There are already tools out there specifically designed to bypass them through paraphrasing, clever prompting, and other trickery.

Best Free Ai Detectors for Teachers

Ok, now we are heading to the main part, which is choosing a tool that can help you navigate this era of AI a little bit easier.

  1. Content at Scale AI Detector

My rating: 7/10

Content at Scale claim that they are 98.3% accurate in detecting AI content. I like that they highlight and provide explanations for each of the sentence in the paragraph.


  • Have the free AI image detector tool to try as a nice add-on.

  • Fast and easy to use.


  • 2500 characters limit.

  • Not accurate enough - I used AI-generated text from Gemini and Claude to test and this tool marked the paragraph as human-written.

If you upgrade to their Paid Plan:

  • Unlimited AI Detection + Paraphrase Analysis

  • 25k undetectable rewrite credits

  • Bulk Undetectable Rewrites

  • Unlimited Image AI Detection

  • Scan by URL

  • Premium Editor

  • Export to Word/Doc/HTML

  1. GPTZero

My rating: 9/10

GPTZero is the first tool that I used when exploring the world of AI. The tool was intuitive, simple but always have more to offer when you come back.


  • To me, this is the best AI detector of all the tools I've tried.

  • GPTZero also offer deep scan and plagiarism check.

  • Chrome extension.


  • 10,000 words limits.

  • Is it just me or is it hard to navigate?

If you upgrade:

  • More words per month

  • Batch file scanning

  • Writing statistic and report

  • Deep AI analysis

  1. ZeroGPT

My rating: 5/10

It's not GPTZero, don't be mistaken. This tool offers AI summarizer, citation generator and more besides its free AI scanner. Out of the bunch, this one offers the worst accuracy - every text generated from AI was marked as human content, which almost makes me feel like they're just trying to console the writer that Yeah, you might be using AI but you're a natural at it.


  • Offer the longest word limit (15000 characters)


  • Like I stated above, the accuracy is meh.

  • The interface is also hard to read.

If you upgrade:

  • Multiple languages support

  • Batch file upload

  • Highlighted sentences (should've included in the Free version BTW)

  • PDF report

And the Best AI Detector for Teacher is:

GPTZero! It almost could pierce through all AI-generated pieces that I paste. Combined with one's own intuitive detective skill, your writers might need to do better in essays in order to bypass the Great Wall.

These 3 above are the tools I've tried, and since GPTZero had worked well for me, there's no reason to try more, but I would appreciate if you can give me the suggestions. This article will be updated regularly!