How plagiarism is checked by different plagiarism checkers
How Plagiarism Is Checked by Different Plagiarism Checkers
Plagiarism checkers are software tools used to detect similarity between a submitted document and existing content available in online and offline databases. Universities, journals, and publishers rely on these tools to ensure academic integrity. Although different plagiarism checkers use different databases and algorithms, their basic working principle remains similar.
1. Basic Working Principle
Most plagiarism checkers work using the following steps:
- Text from the submitted document is extracted
- The text is broken into small segments (phrases or n-grams)
- Each segment is compared with stored databases
- Matching segments are identified
- A similarity percentage is calculated
The final output is shown as a similarity index along with matched sources.
2. Types of Plagiarism Detection Methods
- Exact match detection: Finds identical sentences or phrases
- String matching: Compares word sequences
- Fingerprinting: Converts text into digital signatures for comparison
- Semantic analysis: Detects paraphrased or meaning-based similarity
- Stylometric analysis: Identifies changes in writing style
3. Databases Used by Plagiarism Checkers
Different plagiarism tools use different sources for comparison:
- Internet webpages
- Published journals and books
- Conference proceedings
- Student thesis and dissertations
- Institutional repositories
The size and quality of the database directly affect the detection accuracy.
4. How Popular Plagiarism Checkers Work
Turnitin
- Compares documents with academic databases and student submissions
- Uses advanced string and semantic matching
- Shows similarity with source links
iThenticate
- Mainly used by journals and publishers
- Checks against scholarly articles and paid databases
- Designed for research papers
Grammarly Plagiarism Checker
- Compares with online sources and publications
- Detects direct and paraphrased content
SmallSEOTools / DupliChecker
- Uses web-based search comparison
- Mainly for basic content checking
- Lower database coverage
5. Why Different Checkers Give Different Results
Similarity percentages vary across tools because:
- Each tool has a different database
- Different matching algorithms are used
- Some tools ignore quotations and references
- Some tools detect paraphrasing better than others
- Some exclude common phrases
Therefore, the same document may show different similarity scores in different plagiarism checkers.
6. What Is Actually Considered Plagiarism?
- Copy-pasting without citation
- Improper paraphrasing
- Reusing own published work (self-plagiarism)
- Translating content without reference
- Using figures or tables without permission
7. How Universities Use Plagiarism Reports
- Check total similarity percentage
- Exclude references and quotations
- Analyze matched sources
- Verify originality of ideas
Most universities allow similarity between 10% and 20% depending on policy and discipline.
Conclusion
Plagiarism checkers detect similarity by comparing text segments with massive digital databases using pattern-matching and semantic analysis techniques. Different tools produce different similarity percentages due to differences in their databases and detection algorithms. Understanding how these tools work helps researchers prepare original content and avoid unintentional plagiarism.