Skip to Content

How Accurate is Grammarly Plagiarism Checker

How Accurate is Grammarly Plagiarism Checker

One of the benefits Grammarly premium users have is that they can check the text against 16 billion pages. I have been using Grammarly premium for over three years, and I use the plagiarism checker from time to time.

So, I thought of going all in and reviewing this tool. Is Grammarly plagiarism checker accurate? The article checks five, a PDF document, and a book to see the effectiveness of the Grammarly Plagiarism Checker.

What is Grammarly Plagiarism Checker

It is a plagiarism checker available as part of Grammarly’s premium subscription. It only works in Grammarly’s desktop editor.

How did I take the tests?

So, to make it a fair Grammarly Plagiarism Checker review, I used the service against this website because I don’t have any other websites.

I started my site in 2018, so I will start with one of the articles in 2018 and keep jumping a year in the following tests. After taking the five tests, we will move to a PDF and book. After all the tests, we will count the total score to figure out the accuracy of the Grammarly Plagiarism Checker.

2018 article

Grammarly Plagiarism Checker Test 1

So, in the first test, I took a piece of text from an article published in 2018. In fact, the report is Grammarly vs. Microsoft Word, which was my first article on Grammarly.

Score: Grammarly found the source within a few seconds, so it gets a 100 score.

2019 article

Grammarly Plagiarism Checker Test 2

In the second test, I took an article from 2019. The original publish date was the 1st of June 2019, and since then, the text has not been changed.

Score: Grammarly stood as expected. The final score for this round is 100.

2020 article

Grammarly Plagiarism Checker Test 3

In this test, I took the article from June 2020. The article is on Snapseed and Lightroom apps and has been live since publication.

Score: Grammarly scored 100 out of 100 because it found the content and source.

2021 article

Grammarly Plagiarism Checker Test 4

In 2021, I wrote plenty of articles on Grammarly, but I wanted to ensure that I chose an article and paragraph that had not been changed. So, I found the article Grammarly vs. Linguix, which compares those two programs.

Score: Grammarly did a great job. It got 100 scores on this test as well.

2022 article

Grammarly Plagiarism Checker Test 6

The main stress that comes to plagiarism checkers is when the article is newly published, so I’m taking an article published just 40 days from today.

The article is about two web-based form builder programs called Jotform and Typeform.

Score: Grammarly took 100 out of 100 in this second last test.

Grammarly Plagiarism Checker against PDF

Testing a PDF in Grammarly Plagiarism Checker

To make sure that I’m not leaving anything behind. I took a PDF containing SMS stats. I could not find the publish date for this report, but it looks a few years old.

Score: Grammarly found the text and its source within seconds, getting 100 scores in this round.

Grammarly Plagiarism Checker against a book

Testing a Book in Grammarly Plagiarism Checker

The last test of this Grammarly Plagiarism Checker review is checking the text of a published book on the Project Gutenberg website. The book’s publication date is the 11th of April 2019, which should give Grammarly enough time.

Score: Unfortunately, this time, the Grammarly Plagiarism checker could not check the text source, so it got a 0 score.

Is Grammarly Plagiarism Checker accurate?

After checking Grammarly Plagiarism Checker against articles, a PDF file, and a book, I concluded that Grammarly Plagiarism Checker is 86% effective in finding the plagiarized text and source.

However, like other programs, it’s just a tool and won’t detect if the text is changed manually or by using one of the paraphrasing programs.

How to take advantage of Grammarly Plagiarism Checker

I did a few more tests of my newly published articles for this review. The last article that Grammarly successfully detected was published on the 11th of May, which is just five days past today.

So, regarding articles on the web, it takes Grammarly about a week to crawl and add to its database (considering the article is publicly available on the web). Still, in terms of PDFs and books, the tool may not be fully accurate, as concluded in this review.


Reviewing and testing a program is difficult, as you need data. Although my tests may not fully reveal how accurate the Grammarly Plagiarism Checker is, it sure covers a small picture.

I hope the article helped you see if the plagiarism checker is good. Please take a moment to share your thoughts below as it helps me and others.