Free Toolkit

Text Diff CheckerCompare two texts side by side and see differences highlighted.

Text Diff Checker illustration
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Text Diff Checker

Compare two texts side by side and see differences highlighted.

How to Use
1

Enter Original Text

Paste the original text in the left input area.

2

Enter Modified Text

Paste the modified version in the right input area.

3

View Differences

See additions, deletions, and unchanged lines highlighted in the diff output below.

What Is Text Diff Checker?

A text diff checker compares two versions of text and highlights the differences between them. It uses a line-by-line diff algorithm to identify added lines (shown in green), removed lines (shown in red), and unchanged lines. This is the same type of comparison used in version control systems like Git. The tool shows a unified diff view with statistics on how many lines were added, removed, and left unchanged, making it easy to understand exactly what changed between two versions of any text document.

Why Use Our Text Diff Checker?

  • Visual highlighting of additions, deletions, and unchanged content
  • Line-by-line comparison with unified diff view
  • Statistics showing total added, removed, and unchanged lines
  • Copy the diff output for sharing or documentation
  • Powered by the same algorithm used in Git and other VCS tools

Common Use Cases

Code Review

Compare code changes before committing to identify unintended modifications.

Document Revision

Track changes between document versions to see what was edited, added, or removed.

Contract Comparison

Compare legal or business documents to spot changes between versions.

Configuration Audit

Compare configuration files to identify differences between environments.

Technical Guide

The diff checker uses the Myers diff algorithm (via the "diff" npm library) to compute the minimum set of changes needed to transform one text into another. It operates on a line-by-line basis, producing a list of change objects that indicate whether each segment was added, removed, or unchanged. The algorithm has O(ND) complexity where N is the total length and D is the number of differences, making it efficient for texts with few changes. The output is rendered with color-coded highlighting: green background for added lines, red background with strikethrough for removed lines, and muted color for unchanged context lines. Each line is prefixed with +, -, or space to indicate its change type.

Tips & Best Practices

  • 1
    Paste both versions at once for instant comparison — no button needed
  • 2
    The diff is computed line by line, so even small changes highlight the entire line
  • 3
    Use the Copy Diff button to share changes with colleagues
  • 4
    For character-level diffing within lines, consider using a dedicated code diff tool
  • 5
    The tool handles large texts but may slow down with tens of thousands of lines

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Frequently Asked Questions

QWhat algorithm does it use?
It uses the Myers diff algorithm, the same algorithm used by Git for computing differences between file versions.
QDoes it compare characters or lines?
It compares line by line. If any character in a line differs, the entire line is marked as changed.
QCan I compare code files?
Yes, it works with any plain text including source code, config files, and structured data.
QWhat do the colors mean?
Green (+) indicates added lines, red (-) indicates removed lines, and gray indicates unchanged lines.
QIs there a size limit?
There's no hard limit, but very large texts (100,000+ lines) may cause slower processing.

About Text Diff Checker

Text Diff Checker is a free online tool from FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration required. No ads. Just fast, reliable tools.