Find text overlap

Highlight non-overlapping contiguous character passages shared by two documents without presenting the result as a plagiarism verdict.

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ToolText Overlap Finder
Input
Output
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How it works

A rolling dynamic-programming table finds the longest common substring, masks that span in both documents, and searches again for at most 100 iterations. Coverage is measured in characters and averaged across the two document lengths, while the default 20-character threshold suppresses shorter fragments.

  • Comparison folds case unless case sensitivity is enabled, but highlighted output keeps the original source spelling.
  • Only contiguous sequences qualify; paraphrases and reordered tokens require a different similarity model.

Worked example

Find overlapping text
Detect common passages between two documents
Input
											Source: The quick brown fox jumps over the lazy dog in the park.
Comparison: A fast brown fox jumps over the lazy dog at the zoo.
Output
												Text:  brown fox jumps over the lazy dog 
Source start: 9
Source end: 44
Comparison start: 6
Comparison end: 41

When to use this

Editors locate copied sentences between revisions, maintainers find README boilerplate, and support analysts identify repeated error-message fragments across logs.

Edge cases

  • Reordering two otherwise identical clauses splits them into separate contiguous matches rather than one moved block.
  • A shared 19-character phrase is absent at the default 20-character minimum even when it is the documents’ only overlap.
  • HELLO can match hello in default mode while each highlighted document retains its own capitalization.