I never really gave plagiarism much thought until I almost submitted a paper that accidentally mirrored a source a little too closely.
It wasn’t intentional, but that didn’t matter.
That moment sent me down a rabbit hole, trying to figure out how to make sure my work was truly original without spending hours cross-referencing sources manually.
That’s when I started looking into AI plagiarism checkers.
I tried each one myself. I checked the accuracy level, whether sources were linked or not, paraphrasing tools, and free word limits.
In this guide, I’ll walk you through the 15 best AI plagiarism checkers I tested, what each one does well, and how to pick the right tool for your needs.
Table of Contents
What are AI Plagiarism Checkers?
I always thought plagiarism checkers were just there to catch copy-paste jobs until I used one on something I thought was completely original.
It flagged entire sections.
Not because I copied, but because my AI-generated text sounded too similar to existing content online.
That’s when I realized: modern plagiarism checkers don’t just look for duplicates. They detect patterns, phrasing, and even AI-written content.
So I dug deeper. I tested several AI plagiarism tools, each claiming to catch what others miss.
Keep scrolling to unravel everything!
At a Glance: The Top 15 AI Plagiarism Checkers
| Tool | Accuracy | Track Sources | Free Word Limit | Paraphraser | Cost of Upgrade |
|---|---|---|---|---|---|
| Originality | Excellent | Yes | 1000 words | Yes | Starting from $12.95 per month |
| Copyscape | Excellent | Yes | Unlimited | No | Starting from $4.95 per month |
| QuillBot | Excellent | Paid | 25000 words | Paid | Starting from $4.17 per month |
| Prepostseo | Excellent | Yes | 1000 words | Yes | Free |
| Search Engine Reports | Excellent | Yes | 1000 words | Yes | Starting from $4 per week |
| Smallseotools | Excellent | Yes | 1000 words | Yes | Starting from $4.99 per week |
| Duplichecker | Excellent | Yes | 1000 words | Yes | Starting from $5 per week |
| Plagiarism Checker | Excellent | Yes | 1000 words | Yes | Starting from $8 per month |
| Quetext | Excellent | Yes | 500 words | No | Starting from $13.99 per month |
| Paraphraser | Excellent | No | 1000 words | Yes | Starting from $23 per month |
| PaperRater | Good | Yes | Unlimited | No | Starting from $7.95 per month |
| PapersOwl | Good | Yes | Unlimited | No | Starting from $13.99 per page |
| Grammarly | Good | No | 10,000 characters | No | Starting from $12 per month |
| Ahrefs | Bad | No | 13,112 characters | Yes | Free |
| Plagiarism Check | Excellent | Yes | N/A | No | Starting from $5.99 per month |
How I Tested These AI Plagiarism Checkers
With so many AI plagiarism checkers out there, I didn’t want to just skim reviews or rely on marketing claims.
I wanted to know how these tools *actually* perform when put to the test.
So I did what any curious (and slightly skeptical) writer would do: I ran each tool through a hands-on, side-by-side comparison.
First, I created a sample essay of 1000 words using ChatGPT. I then ran that same paragraph through every plagiarism checker on the list.
This allowed me to see how each tool handled the same input and what kind of results it returned.
But I wasn’t just looking for red flags or simple copy-paste detection. I paid attention to things like:
- Accuracy
- Track sources
- Paraphraser
- Free word limit
By the end of the process, I had a clear picture of which AI plagiarism checkers are helpful and which ones are better left behind.
This review is based entirely on real testing, not assumptions or sponsored hype.
How Do You Choose The Best AI Plagiarism Checkers?
Finding the right AI plagiarism checker took some trial and error.
I needed a tool that was accurate, easy to use, and offered more than just surface-level scanning. So I made a checklist of things that mattered most to me.
Accuracy Matters Most
The first thing I looked for was how accurate the results were. I didn’t want vague matches or false positives.
The best checkers clearly marked copied content and didn’t miss subtle similarities.
Trackable Sources
Good plagiarism tools don’t just say something is copied; they show exactly where it came from.
I preferred checkers that linked to the original sources and highlighted the matching text. That made it easier to fix the problem.
Built-in Paraphraser
Having a paraphrasing tool built in was a big bonus. Instead of switching tools, I could rewrite flagged sections instantly.
Some paraphrasers were basic, but the better ones rewrote full sentences naturally.
Generous Free Word Limit
I always checked how many words I could scan for free.
Tools that allowed at least 1000 words gave me room to test things properly before deciding to upgrade.
The Best 15 AI Plagiarism Checkers (Ranked)
I tested each tool myself to see which ones actually catch plagiarism and offer useful features.
Here are the 15 best AI plagiarism checkers ranked by accuracy, trackable sources, built it- paraphraser, and free word limit.
1. Originality
I tried Originality AI to check if my article was original.
At first, I couldn’t see much without upgrading. It said my content matched 195 websites and had 45 matched phrases.
I paid $12.95 for the monthly plan to see the full results.
Once I upgraded, I could scan entire websites, not just blocks of text. That feature felt powerful.
I also got 2000 credits, which let me check many documents for plagiarism, grammar, spelling, readability, and even SEO.
The results came quickly, and I liked how everything was in one place. I didn’t have to jump between tools.
It felt like a solid choice for writers, bloggers, or anyone needing clear and original content.
Limitation: Not much to see without upgrading to a plan.
This is what I did step by step:
Step 1: I started by going to the Originality plagiarism checker.
Step 2: I entered the text and hit the button Check Plagiarism.
The result showed that the content matched 195 websites and 45 matched phrases.
Step 3: In the free plan, I could only view one matched phrase and the website link.
To view all the matched websites and phrases, I upgraded to the $12.95 per month plan.
It allowed me to scan websites, not just text.
Most importantly, I had 2000 credits to check as many documents as I wanted, including plagiarism, readability, grammar, spelling, and SEO.
2. Copyscape
I started using Copyscape when I needed to check a batch of blog posts for plagiarism. It was fast and easy to use.
But one thing I noticed right away — there’s no built-in paraphraser. So, after checking my content, I had to use another tool to rewrite the copied parts.
To scan multiple pages at once, I upgraded to the premium version. I deposited just $5, and that was enough to get started.
The results were clear, showing exactly where the matches came from.
Copyscape didn’t overwhelm me with features, it focused on what it does best.
If you want a simple and solid plagiarism checker, it gets the job done well.
Limitation: No paraphraser.
This is what I did step by step:
Step 1: After opening the Copyscape plagiarism checker, I pasted my text.
Step 2: Then, hit the Scan Now button.
Step 3: After the results were displayed, I clicked Compare Text for each item detected.
Step 4: A new window opened. It showed me which text was plagiarized so I could change them one by one.
Since Copyscape doesn’t have a built-in paraphraser, I used an external tool to paraphrase the text.
By upgrading to the premium plan, I could check up to 10,000 pages in a single operation.
To scan a bunch of pages, I just deposited $5, and it took care of everything.
3. QuillBot
I gave QuillBot’s plagiarism checker a try when I needed to scan a long article. But right away, I hit a limit — 25,000 words.
It wouldn’t show me the results unless I upgraded. So, I went ahead and paid for the $4.17 per month plan.
Right after upgrading, everything opened up. I could run full plagiarism checks without restrictions.
The results were clear and showed exactly where the copied parts came from. I liked that I could click the source links and see the original pages.
What made it even better was QuillBot’s built-in paraphraser.
I used it to quickly rewrite the flagged parts. It saved me time and effort.
Limitation: Not free.
This is what I did step by step:
Step 1: I opened QuillBot’s plagiarism checker on my browser.
Step 2: After inputting the text in the box, I hit the Scan for plagiarism button.
Step 3: The tool refused to generate the result without me upgrading the plan.
This being the case, I upgraded to the $4.17 per month plan.
As soon as I did that, I was able to view results for plagiarism checks without restrictions.
I could also track the source links of plagiarized content and fix them with QuillBot’s built-in paraphrasing tool.
I was quite happy with the outcome.
4. Prepostseo
I needed to check my assignment for plagiarism and didn’t want to pay for a tool. That’s when I found Prepostseo’s AI Plagiarism Checker.
I uploaded my text, and within seconds, it highlighted the parts that were copied and showed the exact sources. I was surprised at how accurate it was, especially for a free tool.
I didn’t stop there. I used the built-in paraphrasing feature to rewrite the flagged parts.
Then I used the AI humanizer to smooth out the sentences so they felt more natural.
It was easy to use and didn’t ask for a login.
I liked that everything worked in one place— scan, fix, and polish.
It saved me time and stress. Now I always run my work through Prepostseo before submitting anything.
Limitation: None
This is what I did step by step:
Step 1: I started by opening Prepostseo on my browser.
Step 2: I input my text in the empty box and opted for the Check Plagiarism button.
The result showed that 91% of the text has been plagiarized.
Step 3: When I click on a marked sentence, the tool shows the exact source it was copied from.
Step 4: When I clicked on the Remove Plagiarism button, it led me to the paraphrasing tool.
Overall, I was quite satisfied with Prepostseo’s plagiarism checker.
Even though it’s a free tool, it was accurate in detecting plagiarism. It also displayed the sources of copied sentences.
Furthermore, I could remove plagiarism through the paraphrasing tool and polish with the AI humanizer.
5. Search Engine Reports
I tried the AI Plagiarism Checker from Search Engine Reports when I needed to check a short blog post.
It let me upload a file from my computer or even from Dropbox, which was helpful. I liked that I didn’t have to copy and paste everything manually.
There’s a 1000-word limit, but for short pieces, it works fine.
One thing to keep in mind: use Google Chrome. I couldn’t see the captcha in other browsers, which made it frustrating at first.
But once I switched to Chrome, it worked smoothly. I even tested it by entering a blog URL, and it scanned the content right away.
The basic version is free, but if you want a deeper scan, you’ll need to upgrade.
Limitation: Deep plagiarism check is only available after upgrade.
This is what I did step by step:
Step 1: After opening the Search Engine Reports plagiarism checker, I entered my text in the box.
Step 2: Then, hit the Check Plagiarism option.
It settled on a plagiarism score of 86%.
Step 3: And highlighted plagiarized sentences along with direct sources from which the sentences were copied. I could even see the percentages.
To make the results more accurate, I upgraded to the $4 weekly plan.
It allowed me to process 10,000 words per week.
I had access to a deep plagiarism search, a grammar checker, and a citation assistant.
6. SmallSEOTools
When I first tried SmallSEOTools AI Plagiarism Checker, I started with the free version.
It worked okay for short documents, but I quickly hit a limit. The free version only allowed me to check 1,000 words at a time.
If I wanted a deeper scan or a longer document check, I had to upgrade my plan. The premium version lets me check up to 30,000 words in a single go.
One thing I didn’t like about the free version was that I couldn’t choose the tone, mode, or language for paraphrasing.
After upgrading, I could access more features, making my plagiarism checks more efficient and detailed.
Limitation: Upgrade to use deep scan and advanced feature selection.
This is what I did step by step:
Step 1: I accessed the SmallSEOTools plagiarism detector on my browser.
Step 2: Typed the 1000-word essay that I’m using to test all the tools.
Step 3: Pressed Check Plagiarism.
I’m happy that the tool detected 95% of plagiarism.
It also displayed the links to the sources on the right side.
Step 4: I downloaded the report by clicking on the Download Report button.
Step 5: Then, I clicked on the Make It Unique button to see what happened. Thankfully, a new window opened leading to the paraphrasing tool.
Step 6: To paraphrase, I just selected the button Click here.
For a deep plagiarism check, I had to upgrade my plan.
To paraphrase, one downside was that I could not choose the tone, mode, and language in the free version.
Previously, the free version limited me to checking only 1,000 words at a time.
With the premium plan, I could check up to 30,000 words in a single scan.
7. Duplichecker
I tried Duplichecker when I was writing an essay and needed to make sure it was original. It was super easy to use.
I liked that I could also upload files from my computer, Dropbox, or even Google Drive. One time I used a URL to check content from a blog post, and it worked perfectly.
There’s a grammar check option too, which helped clean up my writing.
I could even choose the language and adjust the spin level if I needed to rewrite something.
It’s simple, no account needed, and it did the job fast. I find myself using it often for school and freelance work.
Limitation: 1000 words limit per search.
This is what I did step by step:
Step 1: To begin, I accessed Duplichecker AI Plagiarism Checker on my browser.
Step 2: I pasted the 1000-word essay in the box. Then, I selected Check Plagiarism.
Step 3: The detector accurately identified that the entire content was 100% plagiarized. See it for yourself.
Step 4: Then, I clicked the button Remove Plagiarism to see if the tool would help me with that.
Step 5: I liked that it gave me the option to choose the language and the type of spin I want in the output. Then, I clicked Remove Plagiarism.
Step 6: The new output highlights all the words that have been changed. To finish, I just clicked on the Download and Copy button at the bottom.
It’s a free tool, so there was no need for me to upgrade.
8. Plagiarism Checker
When I first tried the Plagiarism Checker, I didn’t expect much, but it surprised me.
I could upload any file from my computer, Dropbox, or Google Drive, and it scanned everything fast. I remember using it for a long research paper I was nervous about.
In seconds, it showed me the parts that matched online content and gave me links to the sources. That helped me fix things before submission.
The interface was simple, and I didn’t need any training to use it.
I could even run multiple checks in a day without problems. It felt like having a second pair of eyes.
Whether it’s school work or blog posts, this tool has become a must-have in my writing routine.
Limitation: None.
This is what I did step by step:
Step 1: I opened the Plagiarism Checker in my browser.
Step 2: I pasted my essay into the box and selected the Check Plagiarism button.
Step 3: I could see which sentences were plagiarized along with the sources. The tool accurately detected plagiarism as displayed below.
Step 4: I selected the Make it Unique button to see if the tool would let me paraphrase for free.
Step 5: I chose the Standard tone and English as the language, and hit Paraphrase.
Step 6: Finally, I copied the content and used it in my paper.
For $8 per month, I was able to use this tool to check 25,000 words per search.
I could also download PDF reports, log in as different users, and enjoy deep search.
It even highlighted the exact parts of my text that matched online sources.
The deep search scanned academic databases, not just basic websites.
9. Quetext
I recently tried Quetext AI Plagiarism Checker, and it gave me a good start.
The free version lets me check up to 500 words at once. However, once I reached that limit, I had to upgrade if I wanted to use it again.
To get started, I had to sign in with my Google account, which was simple enough.
What I liked most was that it provided direct source links for each plagiarized sentence. This made it easier for me to navigate and address the issues.
It also acted as a free citation generator.
Overall, easy access to source links and citation generation made it a very useful tool, even with the word count limit.
Limitation: Can check up to 500 words at once.
This is what I did step by step:
Step 1: Headed straight to Quetext plagiarism checker’s homepage to get started.
Step 2: I had to sign in with my Google account.
Step 3: After pasting the text, I clicked Check Plagiarism.
Step 4: The plagiarism score was 91%. The sources were displayed nicely on the right-hand side.
Step 5: By clicking on the right and left arrows, I navigated the source links of each plagiarized sentence.
Step 6: What I liked is that by clicking on Cite Source, I can get citation information about the author.
Step 7: The tool created a citation for me after I hit the button Create Citation.
Here’s a sample:
I was satisfied with the free plan, so I didn’t upgrade.
If you wish to, then you may want to go for the $13.99 monthly plan.
This plan will let you check 100,000 words for plagiarism, AI detection, and grammar checking.
10. Plagiarism Check
I tried Plagiarism Check AI when I was editing an article and wanted to be sure it was clean.
I used the free trial, which gave me one check for one page. It wasn’t much, but it was enough to test how it worked.
I pasted my text into the box, and in seconds, it scanned everything.
It also traced the exact sources of my sentences. It showed where each match came from, which made it easy to rewrite the copied parts.
The tool was simple and didn’t feel overwhelming.
Even though the trial was limited, it gave me a good first impression.
Limitation: 1 free check in the trial version.
This is what I did step by step:
Step 1: I opened Plagiarism Check.
Step 2: I entered the words and clicked Check 1 free page.
Step 3: According to the tool, the entire text is plagiarized, which is true.
After upgrading to the $5.99 per month plan, I could check 20 pages without daily limits.
Additionally, I could use the other tools like the citation generator, grammar checker, and AI detector.
11. Paraphraser
I used the Paraphraser AI Plagiarism Checker while working on a small writing project.
The free version let me check up to 1000 words at a time. I later upgraded, but the limit only increased to 2000 words.
The paraphrasing tool only changed one or two words in each sentence. It didn’t feel fully rewritten.
There was also a 400-word limit for paraphrasing, so I had to do it in parts.
It’s not the best for deep rewriting, but it’s a handy tool if you need something quick.
Limitation: Upgrade to remove plagiarism.
This is what I did step by step:
Step 1: I found access to Paraphraser plagiarism checker and immediately input the text I want to check.
Step 2: Once done, I confirmed the captcha and pressed the Check Plagiarism option.
Based on the report, 95% of the content is plagiarized, with the option to download the report.
Step 3: I clicked on Remove Plag, hoping something would happen. But it didn’t work.
Step 4: Since the button didn’t work, I clicked on All Tools to see if there was any paraphrasing tool available.
Step 5: I copied and pasted the plagiarized content into the paraphrasing toolbox.
The paraphrased text wasn’t paraphrased well. The tool only changed 1 or 2 words per sentence.
The free plan allowed plagiarism checks for up to 1000 words, whereas the paid plan only increased that limit to 2000 words.
But I liked the extra tools that came with the upgrade, like the paraphrasing tool.
I used the paraphrasing tool often after upgrading. The paraphrasing limit rose to 2000 words, which I liked.
12. PaperRater
I used PaperRater’s AI Plagiarism Checker for one of my school assignments.
The detection wasn’t the best. It missed a few copied lines I had added on purpose to test it.
But what I liked most was that it showed me exactly which paper my sentence matched.
I hovered over the underlined text, and with one click, I was taken straight to the source. That felt helpful.
The tool worked quickly and didn’t ask me to sign up, which saved time.
It also gave grammar feedback, though some suggestions didn’t make much sense.
It’s not perfect, but if you’re in a rush and want basic help, PaperRater does a decent job. I wouldn’t rely on it alone, though.
Limitation:
Plagiarism detection capacity is average.
This is what I did step by step:
Step 1: I opened the PaperRater AI plagiarism checker on my browser.
Step 2: After entering the 1000-word essay, I smashed the button Check for plagiarism.
Step 3: A window like this popped up. I made sure to click Agree and Continue.
The tool detected 83% plagiarism in the text.
Step 4: By hovering my mouse over the links, I could see which sentences were plagiarized.
Step 5: When I clicked a link, it took me to the original source.
Since there is no paraphraser offered, I decided to use an external Paragraph Rewriter.
PaperRater offered unlimited submissions for $7.95 per month. But I wasn’t impressed with its average plagiarism detection capacity.
So, I decided not to upgrade to the paid plan.
13. PapersOwl
I tried the PapersOwl AI Plagiarism Checker when I was finishing a research paper late at night.
The tool looked simple, and I didn’t need to sign up. I uploaded my text and got the results in seconds.
It highlighted the copied parts and linked them to their sources, which helped me quickly check what needed fixing.
But one thing bugged me: there was no paraphrasing tool.
After seeing what was flagged, I had to go to a different site to rewrite those parts.
The checker itself was decent. It caught most of the copied lines and worked fast. But I wish it had built-in suggestions or a rewrite option.
Limitation: No paraphraser.
This is what I did step by step:
Step 1: I logged into PapersOwl plagiarism checker and pasted my essay topic into the box.
Step 2: Then, I hit Scan for plagiarism.
Based on the result, 74% of the text is plagiarized, which is not necessarily correct.
Step 3: I could also check the sources of the plagiarized sentences on the right side.
Step 4: I clicked the button Make It Unique to see if the tool would let me paraphrase the text.
Unfortunately, I hit a paywall.
What I realized is that I have to hire someone to paraphrase the essay for me.
Since I wasn’t interested in that, I skipped it.
14. Grammarly
I started using the Grammarly AI plagiarism checker almost every day. I could check content up to 10,000 characters, which was more than enough for my essays and articles.
Uploading a file from my computer was simple. It scanned everything in seconds.
One time, I uploaded a research paper, and it found a few lines that matched online sources. That helped me rewrite them before submitting.
What I like most is how smooth it feels. I get grammar suggestions, tone checks, and clarity tips all in one place.
It tells me if my writing sounds too aggressive or too dull.
It’s like having a teacher and editor in one tool. It’s saved me from embarrassing mistakes more than once.
Limitation: Upgrade to fix plagiarized sentences.
This is what I did step by step:
Step 1: I accessed the Grammarly AI Plagiarism Checker in my browser.
Step 2: I typed out the text and clicked Scan for plagiarism.
Step 3: The tool identified 45 writing issues, although there’s no percentage score.
Grammarly wouldn’t let me rewrite plagiarized sentences without going Pro. So I upgraded.
It gave me unlimited personalized suggestions and adjusted my text.
And of course, fixed my grammar!
15. Ahrefs
I recently tried Ahrefs AI Plagiarism Checker, and here’s my experience.
It’s a helpful tool, but it’s not fully automatic.
You need to upload your text, and then the tool scans it.
However, it doesn’t highlight specific sentences that are plagiarized, which makes it harder to pinpoint the exact issues.
For example, with a 1,000-word document, I had to manually check each section to see which sentences were flagged.
If the tool could highlight the suspicious sentences directly, it would have made my job so much easier.
I can see the potential of the tool, but I think it still needs some work to improve its usability.
Limitation: No paraphraser. Detection is not clear.
This is what I did step by step:
Step 1: I opened Ahrefs AI plagiarism checker.
Step 2: I entered my text of about 1000 words and pressed the Scan your content button.
The result was presented quite differently.
It states the suspicious sentences instead of highlighting them. Also doesn’t provide links to the source.
Step 3: I had to find and change the plagiarized sentences manually. Not happy about that.
Step 4: I had to find the Ahrefs paraphrasing tool separately and use it to change the plagiarized text.
I’m not recommending this tool to anybody to check for plagiarism because, frankly, it’s not automatic.
Moreover, it’s not clear how much of the 1000-word text is plagiarized. If the tool highlighted the suspicious sentences, it would’ve helped me.
FAQs
How Accurate Are AI Plagiarism Checkers?
Top AI plagiarism checkers are quite accurate. They detect exact and paraphrased content, but free tools may miss matches or give incomplete reports.
How Does AI Plagiarism Detection Work?
AI tools compare your text against online databases using smart algorithms. They detect similarities, highlight matched content, and often link to sources for easy review and correction.
Is Plagiarism Checker Worth the Money?
Yes, premium plagiarism checkers offer deeper scans, source tracking, and reliable accuracy. They’re worth it for students, writers, and professionals who need original, trustworthy content.
Can I Use Them for Free?
Some checkers offer a free version with limits, like 500 or 1,000 words per check. Full reports or deeper scans often require a subscription.
Do They Detect AI-Generated Text Too?
Certain tools, such as Originality.ai and Copyleaks, can detect AI content as well as plagiarism. You can often scan for both in one go.
How Deep is Plagiarism Scanning?
Effective tools search across academic journals, web archives, and indexed sources, not just surface-level websites.
Bottom Line
After testing so many tools, I found that not all plagiarism checkers work the same. Some were fast but missed things. Others were slow but more accurate.
I looked for tools that showed sources, had good free word limits, and offered helpful extras like paraphrasing.
A few stood out and made the process easy.
I didn’t include the industry leaders Copyleaks and GPTZero in this blog because they don’t support free plagiarism checking, which didn’t meet my criteria.
If you’re like me and care about writing original content, one of the tools in this blog will be a great fit!
