Design Plagiarism Detector
Last Updated: December 24, 2025
What is a Plagiarism Detector?
A plagiarism detector is a system that compares submitted documents against a large corpus of existing content to identify potential instances of copied or insufficiently attributed text.
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The core idea is to break documents into smaller pieces, compute signatures or fingerprints for these pieces, and then efficiently search for matches across billions of stored documents. When matches are found, the system calculates a similarity score and highlights the overlapping sections.
Popular Examples: Turnitin, Copyscape, Grammarly Plagiarism Checker, Quetext
In this chapter, we will explore the high-level design of a plagiarism detection system.
This system design problem combines text processing, similarity algorithms, distributed search, and scalability challenges. It tests your understanding of how to handle large-scale document comparison efficiently.
Lets start by clarifying the requirements.