How Good Is The Grammarly Plagiarism Checker?

Discover how good is the Grammarly Plagiarism Checker based on my extensive tests using this tool. 

I’ve been a Grammarly customer since 2014. Over the years, Grammarly has evolved from a grammar checker into an AI-powered writing assistant. One of its more underrated tools is the plagiarism checker. It’s a Grammarly Premium and Grammarly Business feature. I use this tool regularly to check my work and the work of freelance writers I commission.

I regularly publish content on this website, written by me and written by a team of writers. I also run a series of other content websites. Checking articles for plagiarism by new writers that I’m vetting and ensuring that work published on this site isn’t plagiarized is a key part of the business’s publishing workflow. I’ve tested dozens of plagiarism checkers over the past few years.

As a former journalist and research paper writer, I worry about plagiarism: accidental or otherwise. Perhaps the most high-profile case of plagiarism is the story of New Republic journalist Stephen Glass who was exposed for making stories up and for plagiarism.

The Grammarly plagiarism checker is great for checking content quickly and easily for plagiarism. It’s affordable and easy to use too. However, it’s less suitable for specialist writers, like academics.

How Much Does The Grammarly Plagiarism Checker Cost?

As mentioned in our Grammarly review, its plagiarism checker is premium only. Any writer can try Grammarly for free and use it to find and fix more grammar errors than a traditional grammar checker. However, if you want to use the plagiarism checker, that will cost you $30 per month. However, you can avail of a Grammarly deal and save up to 20%.

If you’re serious about writing and publishing content online or are worried about plagiarism, $30 a month isn’t too much to pay. Even if it’s a once-off project, you can always take out a subscription, use the Grammarly Plagiarism Checker, and cancel when you’re done. 

In comparison, other plagiarism checkers have different pricing models. They require writers to take out a subscription and then purchase additional credits to run a plagiarism check. These credits are based on how many words or pages you want to check for plagiarism. The credit per page or word model is suitable for academics checking research papers, but it’s messier and more confusing for those writing articles regularly. 

The Grammarly Plagiarism Checker comes bundled as part of your monthly subscription, so you don’t have to worry about additional costs. For this reason, I found it’s particularly good if you want to check the writing sample that you’re publishing online at scale for instances of plagiarism. You might be interested in learning what is self-plagiarism.

How The Grammarly Plagiarism Checker Works

Upload some writing or paste it into the Grammarly web app. Next, use Grammarly as a normal to edit your work for grammar mistakes. When done, click on the plagiarism checker on the bottom right of the screen. This button is available in the web app, i.e. not via the plugins or extensions. Grammarly takes a minute to scan your writing against millions of other web pages and content accessible on the internet. Grammarly then assigns a piece of writing a plagiarism percentage score. 

Suppose Grammarly finds sentences or paragraphs in a writing sample similar to what’s published elsewhere. In that case, Grammarly marks the particular section as potentially plagiarized and provides an offending link for an editor or writer to inspect. Then, they can check the offending link, compare both pieces and evaluate if plagiarism is an issue.

What Percentage of Plagiarism is Acceptable on Grammarly?

If a writing sample gets a percentage score less than five per cent, chances are plagiarism isn’t an issue. The writer could have used a term or a name of a popular product, a company, or a service or quoted a freely available source. However, if the score exceeds 10%, go back and rewrite some of the work, include a citation or a link, or check for other issues. Anything about 25% of a red flag.

Limitations of the Plagiarism Checker

The Grammarly Plagiarism Checker works best if it’s comparing a document against content that’s freely available online. That means articles, blog posts, news stories, webpages, and anything anybody can easily access. 

On the other hand, if this content is behind a paywall, for example, an academic paper, a PDF, or a research document, the Grammarly Plagiarism Checker is less likely to identify an instance of potential plagiarism. For this reason, the Grammarly Plagiarism Checker is probably less suitable for academics. They may be better served using a dedicated academic plagiarism checker like Turnitin, or if you can’t access Turnitin, try Scribbr.

What’s The Grammarly Plagiarism Checker Like to Use?

Over the past year or two, I’ve reviewed over a dozen plagiarism checkers. They vary in usability, speed, and intuitiveness. The Grammarly Plagiarism Checker is probably the fastest and easiest to use. All you have to do is open up the web app of Grammarly, paste in the writing sample you want to check, and then click the plagiarism button at the bottom right of the screen. You don’t need to worry about credits or formatting your work. 

With other apps that I’ve tried, these steps are more involved and complicated, and the plagiarism checkers take longer to run. Now, this isn’t a big deal if you’re only checking a couple of documents or perhaps a research paper. Still, if you’re checking dozens of articles each week or each month, then it can quickly become time-consuming and laborious to purchase additional credits. 

Grammarly Plagiarism Checker Tests

Here’s how I tested the Grammarly plagiarism checker for this article. I pasted several pieces that attract a sizeable amount of web traffic for this site. I also checked several articles by freelancers who write content for me. 

Test 1: Checking For Accidental Plagiarism

When I checked one of my articles for plagiarism, I was shocked to find Grammarly flagged it as 97% plagiarism. Grammarly surfaced a link to another website whereby a publisher had taken the entirety of my article and published it on their site without permission. I immediately issued a Google DMCA takedown request. I spotted this issue because of the Grammarly Plagiarism Checker. 

Test 2: Vetting a Freelancer

I run another website in the food and drinks niche. I hired another writer and was impressed by his ability to deliver content quickly. However, when I checked these articles for plagiarism, Grammarly identified issues. Although the entirety of the work wasn’t plagiarised, the writer had copied sections from similar sites online without rewriting, adding his interpretations and attributing them correctly. I immediately fired the writer, rewrote the offending pieces, and added missing citations. 

Test 3: Finding Missing Citations

The Grammarly Plagiarism Checker is great for finding missing citations. I regularly write nonfiction articles and nonfiction business books. Sometimes I want to use an interesting statistic, a fact, or a quote, but I don’t have the source to hand. Using the Grammarly Plagiarism Checker, I can paste this statistic fact or quote, and Grammarly surfaces the original link. This way, I can include the correct link or citation for the author in question and avoid an instance of accidental plagiarism and

I particularly like that Grammarly has started to roll out a citation manager. This enables me to generate citations for my work based on some journals quickly. It currently supports APA, MLA, and the Chicago Manual of Style. I also like the Grammarly Plagiarism Checker because it’s helped me with DMCA takedown requests.

Grammarly Limitations

As helpful as the Grammarly plagiarism checker is, there’s a caveat. You can check individual articles, but it is less suitable for checking articles at scale or monitoring your site passively. For that, I recommend using Copyscape. It’s better at preventing content in bulk. To learn more, read our Copyscape review. 

The Grammarly Plagiarism Checker is less useful for academics who want to avoid plagiarism because of how an accusation could affect the integrity of their work. The Grammarly plagiarism checker can’t scan research papers, PDFs and other pieces of gated content. It also doesn’t compare a paper against works that appear in books and other academic journals. If you’re concerned with this, you’re better off using an academic plagiarism checker like TurnItIn or Scribbr. To learn more, read our Grammarly vs TurnItIn comparison.

Is Grammarly Reliable for Plagiarism Check?

Based on our extensive tests, the Grammarly Plagiarism Checker is a valuable and reliable plagiarism tool for most general writers. It’s quick and easy to use, can help avoid accidental plagiarism, find missing citations, and improve the quality of your work. However, if you have special requirements, for example, in academia, you’re better off using a tool that can scan books and gated content. For an overview of our recommendations, read our guide to the best plagiarism checkers, where I profile the pros and cons of what’s on the market today.