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Diff Checker — Text Compare

Compare two texts side-by-side and see the differences highlighted. Find added, removed, and unchanged lines instantly.

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How to Use

  1. 1

    Paste the original text

    Enter the original version of your text in the left panel.

  2. 2

    Paste the modified text

    Enter the changed version in the right panel.

  3. 3

    Click Compare

    The tool highlights added lines (green), removed lines (red), and unchanged lines with line numbers from both versions.

What is Diff Checker?

A diff checker compares two pieces of text and highlights the differences between them. Lines that exist only in the original are marked as removed, lines that exist only in the modified version are marked as added, and lines that are the same in both are shown as unchanged.

Diff checking is fundamental to software development — it powers git diff, pull request reviews, merge conflict resolution, and code review tools. Beyond code, it's useful for comparing configuration files, document versions, API responses, and any text that changes over time.

This tool uses a standard LCS (Longest Common Subsequence) algorithm to compute the minimal set of changes between two texts, similar to the Unix diff command and the algorithms used by Git.

FAQ

What algorithm does this use?
The tool uses a Longest Common Subsequence (LCS) based diff algorithm, which is the same fundamental approach used by Git and the Unix diff command. It finds the minimal set of changes needed to transform the original text into the modified text.
Can I compare code files?
Yes, the diff checker works with any text — code, configuration files, prose, CSV data, or any other plain text format.
Is there a size limit?
The tool works well with texts up to several thousand lines. Very large files (10,000+ lines) may be slow because the LCS algorithm is O(n×m) in time and space.

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