Can You Trust Your Plagiarism Checker: Are Plagiarism Checkers Accurate?

Are plagiarism checkers accurate?

Will they catch your tiny citation missteps?

Can you fool them?

To answer these questions, you need to understand how online plagiarism checkers work and why they often produce different results. At first glance, all services seem identical. They scan your copy and return the percentage of the plagiarized text (or originality percentage). But if you check the same essay or research paper using different services, the results will be anywhere from 0% to 100% plagiarism. It all comes down to two deciding factors: the database used and the efficiency of the scanning method.

Database Size

To locate plagiarism, online plagiarism checkers compare your piece to others in their database. The more extensive the database, the higher the chances of discovering similarities. Most free services have limited content collections, so they are prone to giving false negative results (0% plagiarism even if some is present). Premium services usually rely on large databases of websites, academic and scientific sources, so their results are more precise.

At the same time, premium plagiarism checkers are known to keep and use any works you check, thus expanding their databases. So when you’re asking, ‘Are plagiarism checkers safe?’ you’re probably worried about getting your paper flagged by your school after you check it before submission. Turnitin is among the most well-known culprits that has caused problems for many students and researchers alike. To avoid trouble, read the checker’s terms and conditions carefully to ensure your copy isn’t stored.

plagiarism checker

Scanning Algorithm

The easiest way to check for plagiarism is by splitting your paper into tiny pieces and comparing them to the database entries on the same topic. However, such algorithms are only good for locating copypasted fragments. They are not sensitive to slapdash rewriting, where you replace words with synonyms wherever possible. Most websites that check your essays for free rely on this scanning algorithm. The most useless ones can falsely flag your properly cited quotes as plagiarism.

More advanced services analyze the underlying structure of sentences and paragraphs and identify paraphrased pieces. However, there’s also a chance for false positive results (high plagiarism percent even if none is present) if some sources heavily influence your writing style. Still, as plagiarism checkers incorporate machine learning and become more advanced, they get better at locating the sources of your rewrites. But quality analysis comes at a price few students are willing to pay, so schools usually cover the cost and run the checks.

What Plagiarism Checkers Don’t Flag

Do plagiarism checkers work on anything?

If that’s the question running through your mind, you’re probably looking for ways to get around a thorough check. I have some good news for you: while plagiarism checkers are getting more advanced, there are still some gaps in their capabilities students exploit with mixed success.

Translations, Rewrites, Images

As we’ve established, a basic uniqueness checker cannot handle a simple rewrite. But even advanced services will not flag plagiarism if you’re thorough enough in your paraphrasing. The translated text is also notoriously difficult to analyze. Using a computer-aided translator with heavy editing is another way students can sometimes get around plagiarism checkers.

Additionally, while text recognition is improving, most plagiarism checkers cannot analyze images. Still, they will raise the alarm if your paper contains images with no text.

Internal Databases

Suppose your school uses an internal offline plagiarism checker to compare your papers to those of other students. In that case, there’s a chance your essays and research papers do not make it beyond the internal database. And if the checker for teachers does not use outside sources to assess uniqueness, your chances of getting away with plagiarism are higher. At the same time, most universities share databases with other schools, minimizing the risk of plagiarism among their students.


Is It Safe to Check for Plagiarism Online?

Yes, but only if you pick a reliable plag checker that does not steal your copy or keep it in the database to cause you trouble later.

Can You Detect Plagiarism Without a Plag Checker?

Sure, many professors can spot plagiarism at ten paces, as they are intimately familiar with the most common sources students use and can identify the borrowed quotes, passages, and style without software. Still, most will need a plag report to substantiate any academic dishonesty accusations against you.

Can I Check My Essay for Plagiarism for Free Online?

You can, though most free services are prone to giving false negatives because of their weak scanning algorithms and small databases. And they may store and use your essay afterward.

How Does Plagiarism Detection Work?

The software analyzes your piece and compares it in small increments to other entries in the database. All identical fragments are considered plagiarism if they are not appropriately cited. Some checkers can also locate weak paraphrasing efforts thanks to machine learning.

Can I Scan My Research Paper for Plagiarism for Free?

Yes, you can, though I do not recommend it. Free services may steal your work or keep it in their databases to produce false positive results when your school reruns the check.

Do Plagiarism Checkers Store Your Work?

Turnitin does, as do several others. Grammarly and others don’t. Read the Terms of Use to know for sure before you sign up for a premium account and run a plag check.

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