15 Accurate AI Plagiarism Checkers to Ensure Original Writing

An AI plagiarism checker is an integral application for any business. With content being the currency of digital marketing, it is important to be able to rest assured that every piece you publish on your website or anywhere is uniquely yours. 

What is an AI Plagiarism Checker?

These tools check your text against various web sources and other directories for plagiarism. They can figure out if you copied sentences or sections from other sources and what kind of alterations you’ve made. 

An AI plagiarism checker often leverages artificial intelligence to discover plagiarism, but please note that these tools aren’t AI checkers per se and thus can’t help you determine if something was written by artificial intelligence. Nevertheless, many of these programs include AI checkers as secondary features and tools. If you are interested in my recommendations for AI checkers, make sure you check out my post on 15 Recommended AI Content Detector Tools.

Why Would I Need an AI Plagiarism Checker?

AI plagiarism checkers are vital for avoiding Google penalties. The search engine has tough policies against plagiarized content, preventing such pieces from ranking. As such, every SEO team should subscribe to one of these programs.

Furthermore, if you’re a big blogger, people will eventually figure out if you’re stealing posts from other sources. Plagiarism, in itself, raises numerous ethical questions and can have a bad impact on your brand’s reputation and authority. 

Being too reliant on plagiarism might also affect your content quality. If you’re blindly copying posts from other sources, there’s a chance you’ll take a few pieces that aren’t that great. So, even if people don’t notice plagiarism, your business might still suffer. 

Plagiarism checkers are thus most important for companies who outsource any of their blogging or copywriting to other companies or people. I have been a religious user of these tools for more than a decade.

15 AI Plagiarism Checkers to Check Out

To help you out, I’ve made a list that highlights incredible paid tools and free, easy-to-use tools. That way, everyone can find an AI plagiarism checker that suits their needs.

1. Copyscape

When we talk about powerful checkers that rely on advanced algorithms, it doesn’t get better than Copyscape. This plagiarism tool has been at the top of that market for years, and I use it regularly for my guest bloggers. The software works great for just about any piece of content, ranging from blog posts to academic writing, essays, and more. 

After copy-pasting your URL, the software will check the web for plagiarized content. It will generate a list of all URLs on the web and highlight sections and sentences that are the same as yours. It’s worth mentioning that Copyscape doesn’t work for AI-generated content. My favorite feature is Copysentry, which sends out automatic notifications to the user.

2. Pro Writing Aid

Pro Writing Aid is a comprehensive tool that combines the technologies of several other programs. The solution relies on artificial intelligence to check any piece of content, highlighting grammar errors,  overused words, readability, and style. I proudly say that I use it all the time when writing books. 

The online tool analyzes your text and provides you with a plagiarism score by comparing your piece with other online content. The program tells you how much unoriginal content is quoted and how much is unquoted. You can also see the total number of issues you need to fix. 

The content detector tool is quite awesome, and it can help you on a daily basis. If you haven’t subscribed to any other writing tools or checkers (i.e., Grammarly, Copyscape), it might be worth it to get this software for all your marketing needs.

3. Originality.ai

Originality.ai is mostly known as software that tracks down machine-written content. In fact, I’ll go as far as to say this is the most popular tool within this particular category. I use it all the time to check how my content writers are doing and whether they’re getting flagged by algorithms. 

Originality.ai can also assist you in detecting plagiarism issues within your original content. It goes back to its database, and relevant online sources are searched to determine whether your text is original. Like most other programs on the list, it will flag any similarities with third-party online articles.  

My favorite thing about this software is how much information you get during a plagiarism scan. Besides checking the text for originality, it will also show the number of characters, paragraphs, sentences, and so on. You can also see a keyword density breakdown, which prevents search algorithm penalties and unoptimized content.

Further Reading: 19 Incredible AI Content Writers (2025)

4. Quillbot

Quillbot was originally an AI-based paraphrasing tool that added numerous features over time. Today, you can use the platform to check your grammar, enhance text as you type, detect AI, summarize text, generate citations, and summarize articles. The software is useful to just about anyone, from marketers to professional writers and university staff. 

Quillbot checks your text for unintentional plagiarism. Besides the overall score, you can see the percentage of text that is identical to other online posts. You can also see minor changes (places where you didn’t fully plagiarize but used synonyms). When the tool finishes, it will show you the number of similar words you might consider changing.

An excellent thing about this software is that it streamlines your writing process. Even if it detects duplicate content, you can easily fix the issue with an AI generator. Then, if you’re flagged for AI writing, you can rephrase the article once again to make it right. 

5. Simplified

Simplified is a comprehensive platform that hinges on artificial intelligence. Besides generating writing, you can use it to generate videos, design, and manage your social media. As such, it’s very popular among large marketing teams. 

The platform’s AI plagiarism checker works as a built-in tool. While you’re on the AI generation screen, you can mark the text and perform several actions, such as rephrasing or summarizing the text. When you click on the “Plagiarism check” button, the software will immediately compare your article or section with other web sources.

Simplified shows you the number of identical words and the percentage of the article that is plagiarised. Then, you can click on the link to check the other text. The software is based on Copyscape technology, which ensures maximum efficiency. 

6. Grammarly

Grammarly is an incredible software that improves your writing style and points out grammar errors and other textual imperfections. Recently, the company has added a few AI functions that further improve the tool’s offering.

After running the scan, Grammarly provides a link to the text that is similar to yours. It gives you the percentage of plagiarism so you can better understand the level of infraction. 

I don’t like Grammarly’s plagiarism checker that much. It’s somewhat slow compared to other solutions I’ve tried, and it doesn’t give you that much data. Still, as a platform, it remains one of the must-have solutions for content teams.

7. Copyleaks

Copyleaks is another one of the big hitters in this market. In my opinion, if you’re looking for a tool for just plagiarism checks, this might be the best option at your disposal. 

Aside from checking your piece against polished web content, it can also compare two articles against each other. You can copy-paste textual files, insert text directly into the box, or select a specific URL. Perhaps the most unique thing about Copyleaks is that it can check any source code for plagiarism. 

I like that you can choose which source you’ll check your article against. The available options include internet content, internal databases, and repositories. Among others, you can ignore quotes and references so that the tool doesn’t flag something that you know isn’t original content. 

Further Reading: AI Content Assistants: 13 Tools to Assist in Your Content Creation

8. Small SEO Tools

As the name indicates, this is a website that provides numerous small tools to its visitors. You can use a paraphrasing tool, reverse image search, grammar checker, and a few other nifty programs. The best thing yet is that most of them have free basic functionality (although with some limitations).

The plagiarism software is rather simple and straightforward. It runs your piece against other web sources and shows you which sections were problematic. While I love that this is a free tool, its slow speed and word limitation might force you to seek out something a bit different. 

9. Dupli Checker

Dupli Checker has several similarities to Small SEO Tool’s checker. Both programs limit you to 1,000 words and both are free yet slow. The program flags any sentences or sections that are unoriginal and provides you links to the original pages. 

Given that Dupli Checker platform also comes with AI and grammar checker, you can perform full analysis within the same dashboard. Once you’re done, you can download the file in PDF or Word format.  

10. Scribbr

Scribbr advertises itself as a free tool. However, as soon as you start using it, you’ll notice a few limitations that make the free version somewhat useless. 

The software will only tell you if there’s a low, medium, or high chance of plagiarism and mention the number of errors. But as you can’t access this data, you won’t know what you did wrong. In other words, it’s one of those fake free software which irritates me to no end. While the premium model is not that bad, I can’t support this method of doing business. 

11. Quetext

Quetext is a simple, free tool that checks up to 500 words of your content. Because of that, it’s a few steps below Dupli Checker and Small SEO Tools checker. My main issue with this software is that it’s rather slow, even when compared to the two previous programs. 

After checking your article against numerous web sources and its vast database, Quetext will mark all sections that are potentially plagiarised. You’ll also see the percentage of how much you’ve copied from these sources. 

Further Reading: 15 Best AI Text Generators (Free and Paid)

12. Plagiarism Detector

This particular detector is just one among numerous free, basic plagiarism checkers. It allows you to analyze 1,000 words of your text, and for more, you’d have to subscribe to the paid plan. 

For a free tool, it’s rather nice. It creates a list of all the pieces you’ve taken from and highlights problematic sentences in your text. The tool also shows the number of characters and words in your text and how much it takes to read it. Plagiarism Detector allows you to download a report for later use.

13. Plagium

As one of the most straightforward tools on this list, Plagium can be of great assistance to smaller writing and marketing teams. The software gives you the option of doing basic and deep searches (if you want more precision). Based on my testing, the basic search does just fine and provides incredibly fast results.

As for the outputs, the information provided is similar to that of other tools. The program highlights all the issues and provides links to original sources. There’s also an AI detector on the page, so you can perform both types of checkups simultaneously. 

14. Smodin

Smodin is a large platform that offers numerous writing solutions. It comes with an AI detector and grader, equation solver, article rewriter, and a few other tools. As for the plagiarism checker, it’s one of the more sophisticated solutions I’ve come across, especially when we consider it’s free to use.

You can perform a slower or faster search, depending on what type of accuracy you need. You can also perform a Google Scholar search and include or exclude certain URLs. There’s an option to change your language, compare the piece with other articles, and perform AI detection. 

Although the free Smodin version has a 1,500-word limit, you won’t feel it that much when analyzing content. That being said, this software can easily replace Copyscape and some other, premium programs.

Further Reading: 15 Powerful AI Blog Writers (When You Need Help Blogging) 

15. PlagiarismCheck.org

With this program, you can detect different tricks people use to mask plagiarism. Besides direct sentence copies, you can find sections where words were rearranged or substituted and where the author used extra symbols to make the piece slightly unique. 

The software is especially great at detecting false positives. One thing that separates this tool from the rest is that PlagiarismCheck.org highlights sections based on direct plagiarism, quote plagiarism, and reference plagiarism. That way, you can differentiate between sentences that were copied for article improvement and those where the author was lazy. 

Next Steps

Plagiarism checkers are something every business can benefit from. Given that we’re all dependent on content marketing, you need a checker that will ensure all your pieces are original and provide your own unique and branded value to your readers. 

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