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Text Diff Checker - Compare Two Texts Online

Text Diff Checker

Compare two texts and see the differences.

What is Text Diffing?

Text diffing (or text comparison) is the process of finding differences between two versions of text. It's essential for tracking changes in documents, code reviews, plagiarism detection, and version control systems. This tool highlights what was added, removed, or changed between two pieces of text.

How Text Diff Works

Text comparison algorithms analyze both texts and identify:

Additions

Text that appears in the modified version but not in the original. Shown in green.

Deletions

Text that was in the original but removed in the modified version. Shown in red.

Changes

Lines that were modified. Shows both the old and new content highlighted in yellow.

Common Use Cases

Developers use diff tools to review code changes before merging. This helps identify bugs, security issues, and ensure coding standards are followed. Tools like GitHub, GitLab, and Bitbucket all have built-in diff viewers.

Writers, editors, and legal professionals use text comparison to track changes in contracts, manuscripts, and official documents. It ensures nothing important was accidentally deleted or modified.

Educators and publishers compare submitted work against original sources to detect copying. High similarity scores may indicate plagiarism that requires further investigation.

System administrators compare configuration files before and after changes to understand exactly what was modified. This is crucial for troubleshooting and audit trails.

Understanding Similarity Percentage

The similarity score indicates how much text remains unchanged between the two versions:

Similarity Interpretation Example Scenario
90-100% Nearly identical Minor typo fixes, small edits
70-90% Mostly similar Sentence rewrites, paragraph additions
50-70% Significant changes Major revisions, restructuring
0-50% Mostly different Complete rewrites, different content

Diff Algorithms

Several algorithms can compute text differences:

  • Longest Common Subsequence (LCS): Finds the longest sequence of characters common to both texts. Most diff tools use variations of this.
  • Myers' Algorithm: Efficient algorithm used by Git and Unix diff. Finds minimal edit distance.
  • Patience Diff: Better for code; matches unique lines first, reducing noisy diffs.
  • Histogram Diff: Similar to Patience but faster; used by JGit.

Tips for Better Diff Results

  • Consistent formatting: Remove extra whitespace and use consistent line breaks before comparing
  • One change at a time: When making edits, commit or save frequently for clearer diff history
  • Use semantic diffing: For code, consider language-aware diff tools that understand syntax
  • Ignore whitespace: Many tools offer options to ignore whitespace-only changes

Version Control Integration

Text diff is the foundation of version control systems:

# Git diff commands
git diff                  # Compare working directory to staging
git diff --staged        # Compare staging to last commit
git diff HEAD~1          # Compare to previous commit
git diff branch1..branch2 # Compare two branches

Git stores changes as diffs (called "deltas") rather than full file copies, making repositories efficient.

Diff Legend

Green Added text

Red Removed text

Yellow Modified text

Pro Tips
  • Paste original in left, modified in right
  • Trim whitespace for cleaner diffs
  • Compare line by line for code
  • Check for subtle changes in high-similarity texts
Popular Diff Tools
  • diff (Unix): Command-line classic
  • WinMerge: Windows GUI tool
  • Meld: Cross-platform visual diff
  • Beyond Compare: Professional tool
  • VS Code: Built-in diff viewer
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